2022/05/19 更新

写真a

テズドゥヤー タイフン
テズドゥヤー タイフン
所属
理工学術院 大学院創造理工学研究科
職名
教授(任期付)
ホームページ

学内研究所等

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学位

  • カリフォルニア工科大学   博士

 

論文

  • Space–time computational analysis of tire aerodynamics with actual geometry, road contact, tire deformation, road roughness and fluid film

    Kuraishi T, Takizawa K, Tezduyar T.E

    Computational Mechanics   64 ( 6 ) 1699 - 1718  2019年12月  [査読有り]

    DOI

  • Space–time VMS flow analysis of a turbocharger turbine with isogeometric discretization: computations with time-dependent and steady-inflow representations of the intake/exhaust cycle

    Otoguro Y, Takizawa K, Tezduyar T.E, Nagaoka K, Avsar R, Zhang Y

    Computational Mechanics   64 ( 5 ) 1403 - 1419  2019年11月  [査読有り]

    DOI

  • Computational analysis of performance deterioration of a wind turbine blade strip subjected to environmental erosion

    Castorrini, Alessio, Corsini, Alessandro, Rispoli, Franco, Venturini, Paolo, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   64 ( 4 ) 1133 - 1153  2019年10月  [査読有り]

     概要を見る

    Wind-turbine blade rain and sand erosion, over long periods of time, can degrade the aerodynamic performance and therefore the power production. Computational analysis of the erosion can help engineers have a better understanding of the maintenance and protection requirements. We present an integrated method for this class of computational analysis. The main components of the method are the streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) stabilizations, a finite element particle-cloud tracking method, an erosion model based on two time scales, and the solid-extension mesh moving technique (SEMMT). The turbulent-flow nature of the analysis is handled with a Reynolds-averaged Navier-Stokes model and SUPG/PSPG stabilization, the particle-cloud trajectories are calculated based on the computed flow field and closure models defined for the turbulent dispersion of particles, and one-way dependence is assumed between the flow and particle dynamics. Because the geometry update due to the erosion has a very long time scale compared to the fluid-particle dynamics, the update takes place in a sequence of "evolution steps" representing the impact of the erosion. A scale-up factor, calculated in different ways depending on the update threshold criterion, relates the erosions and particle counts in the evolution steps to those in the fluid-particle simulation. As the blade geometry evolves, the mesh is updated with the SEMMT. We present computational analysis of rain and sand erosion for a wind-turbine blade strip, including a case with actual rainfall data and experimental aerodynamic data for eroded airfoil geometries.

    DOI

  • Computer Modeling of Wind Turbines: 1. ALE-VMS and ST-VMS Aerodynamic and FSI Analysis

    Korobenko, Artem, Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   26 ( 4 ) 1059 - 1099  2019年09月  [査読有り]

     概要を見る

    This is the first part of a two-part article on computer modeling of wind turbines. We describe the recent advances made by our teams in ALE-VMS and ST-VMS computational aerodynamic and fluid-structure interaction (FSI) analysis of wind turbines. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian-Eulerian method. The VMS components are from the residual-based VMS method. The ST-VMS method is the VMS version of the Deforming-Spatial-Domain/Stabilized Space-Time method. The ALE-VMS and ST-VMS serve as the core methods in the computations. They are complemented by special methods that include the ALE-VMS versions for stratified flows, sliding interfaces and weak enforcement of Dirichlet boundary conditions, ST Slip Interface (ST-SI) method, NURBS-based isogeometric analysis, ST/NURBS Mesh Update Method (STNMUM), Kirchhoff-Love shell modeling of wind-turbine structures, and full FSI coupling. The VMS feature of the ALE-VMS and ST-VMS addresses the computational challenges associated with the multiscale nature of the unsteady flow, and the moving-mesh feature of the ALE and ST frameworks enables high-resolution computation near the rotor surface. The ST framework, in a general context, provides higher-order accuracy. The ALE-VMS version for sliding interfaces and the ST-SI enable moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the sliding interface or the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-SI also enables prescribing the fluid velocity at the turbine rotor surface as weakly-enforced Dirichlet boundary condition. The STNMUM enables exact representation of the mesh rotation. The analysis cases reported include both the horizontal-axis and vertical-axis wind turbines, stratified and unstratified flows, standalone wind turbines, wind turbines with tower or support columns, aerodynamic interaction between two wind turbines, and the FSI between the aerodynamics and structural dynamics of wind turbines. Comparisons with experimental data are also included where applicable. The reported cases demonstrate the effectiveness of the ALE-VMS and ST-VMS computational analysis in wind-turbine aerodynamics and FSI.

    DOI

  • Medical-image-based aorta modeling with zero-stress-state estimation

    Sasaki, Takafumi, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   64 ( 1 ) 249 - 271  2019年07月  [査読有り]

     概要を見る

    Because the medical-image-based geometries used in patient-specific arterial fluid-structure interaction computations do not come from the zero-stress state (ZSS) of the artery, we need to estimate the ZSS required in the computations. The task becomes even more challenging for arteries with complex geometries, such as the aorta. In a method we introduced earlier the estimate is based on T-spline discretization of the arterial wall and is in the form of integration-point-based ZSS (IPBZSS). The T-spline discretization enables dealing with complex arterial geometries, such as an aorta model with branches, while retaining the desirable features of isogeometric discretization. With higher-order basis functions of the isogeometric discretization, we may be able to achieve a similar level of accuracy as with the linear basis functions, but using larger-size and fewer elements. In addition, the higher-order basis functions allow representation of more complex shapes within an element. The IPBZSS is a convenient representation of the ZSS because with isogeometric discretization, especially with T-spline discretization, specifying conditions at integration points is more straightforward than imposing conditions on control points. The method has two main components. 1. An iteration technique, which starts with a calculated ZSS initial guess, is used for computing the IPBZSS such that when a given pressure load is applied, the medical-image-based target shape is matched. 2. A design procedure, which is based on the Kirchhoff-Love shell model of the artery, is used for calculating the ZSS initial guess. Here we increase the scope and robustness of the method by introducing a new design procedure for the ZSS initial guess. The new design procedure has two features. (a) An IPB shell-like coordinate system, which increases the scope of the design to general parametrization in the computational space. (b) Analytical solution of the force equilibrium in the normal direction, based on the Kirchhoff-Love shell model, which places proper constraints on the design parameters. This increases the estimation accuracy, which in turn increases the robustness of the iterations and the convergence speed. To show how the new design procedure for the ZSS initial guess performs, we first present 3D test computations with a straight tube and a Y-shaped tube. Then we present a 3D computation where the target geometry is coming from medical image of a human aorta, and we include the branches in the model.

    DOI

  • Tire aerodynamics with actual tire geometry, road contact and tire deformation

    Kuraishi, Takashi, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   63 ( 6 ) 1165 - 1185  2019年06月  [査読有り]

     概要を見る

    Tire aerodynamics with actual tire geometry, road contact and tire deformation pose tough computational challenges. The challenges include (1) the complexity of an actual tire geometry with longitudinal and transverse grooves, (2) the spin of the tire, (3) maintaining accurate representation of the boundary layers near the tire while being able to deal with the flow-domain topology change created by the road contact and tire deformation, and (4) the turbulent nature of the flow. A new space-time (ST) computational method, ST-SI-TC-IGA, is enabling us to address these challenges. The core component of the ST-SI-TC-IGA is the ST Variational Multiscale (ST-VMS) method, and the other key components are the ST Slip Interface (ST-SI) and ST Topology Change (ST-TC) methods and the ST Isogeometric Analysis (ST-IGA). The VMS feature of the ST-VMS addresses the challenge created by the turbulent nature of the flow, the moving-mesh feature of the ST framework enables high-resolution flow computation near the moving fluid-solid interfaces, and the higher-order accuracy of the ST framework strengthens both features. The ST-SI enables moving-mesh computation with the tire spinning. The mesh covering the tire spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-TC enables moving-mesh computation even with the TC created by the contact between the tire and the road. It deals with the contact while maintaining high-resolution flow representation near the tire. Integration of the ST-SI and ST-TC enables high-resolution representation even though parts of the SI are coinciding with the tire and road surfaces. It also enables dealing with the tire-road contact location change and contact sliding. By integrating the ST-IGA with the ST-SI and ST-TC, in addition to having a more accurate representation of the tire geometry and increased accuracy in the flow solution, the element density in the tire grooves and in the narrow spaces near the contact areas is kept at a reasonable level. We present computations with the ST-SI-TC-IGA and two models of flow around a rotating tire with road contact and prescribed deformation. One is a simple 2D model for verification purposes, and one is a 3D model with an actual tire geometry and a deformation pattern provided by the tire company. The computations show the effectiveness of the ST-SI-TC-IGA in tire aerodynamics.

    DOI

  • Aorta zero-stress state modeling with T-spline discretization

    Sasaki, Takafumi, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   63 ( 6 ) 1315 - 1331  2019年06月  [査読有り]

     概要を見る

    The image-based arterial geometries used in patient-specific arterial fluid-structure interaction (FSI) computations, such as aorta FSI computations, do not come from the zero-stress state (ZSS) of the artery. We propose a method for estimating the ZSS required in the computations. Our estimate is based on T-spline discretization of the arterial wall and is in the form of integration-point-based ZSS (IPBZSS). The method has two main components. (1) An iterative method, which starts with a calculated initial guess, is used for computing the IPBZSS such that when a given pressure load is applied, the image-based target shape is matched. (2) A method, which is based on the shell model of the artery, is used for calculating the initial guess. The T-spline discretization enables dealing with complex arterial geometries, such as an aorta model with branches, while retaining the desirable features of isogeometric discretization. With higher-order basis functions of the isogeometric discretization, we may be able to achieve a similar level of accuracy as with the linear basis functions, but using larger-size and much fewer elements. In addition, the higher-order basis functions allow representation of more complex shapes within an element. The IPBZSS is a convenient representation of the ZSS because with isogeometric discretization, especially with T-spline discretization, specifying conditions at integration points is more straightforward than imposing conditions on control points. Calculating the initial guess based on the shell model of the artery results in a more realistic initial guess. To show how the new ZSS estimation method performs, we first present 3D test computations with a Y-shaped tube. Then we show a 3D computation where the target geometry is coming from medical image of a human aorta, and we include the branches in our model.

    DOI

  • Space-time isogeometric flow analysis with built-in Reynolds-equation limit

    Kuraishi, Takashi, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   29 ( 5 ) 871 - 904  2019年05月  [査読有り]

     概要を見る

    We present a space-time (ST) computational flow analysis method with built-in Reynolds-equation limit. The method enables solution of lubrication fluid dynamics problems with a computational cost comparable to that of the Reynolds-equation model for the comparable solution quality, but with the computational flexibility to go beyond the limitations of the Reynolds-equation model. The key components of the method are the ST Variational Multiscale (ST-VMS) method, ST Isogeometric Analysis (ST-IGA), and the ST Slip Interface (ST-SI) method. The VMS feature of the ST-VMS serves as a numerical stabilization method with a good track record, the moving-mesh feature of the ST framework enables high-resolution flow computation near the moving fluid-solid interfaces, and the higher-order accuracy of the ST framework strengthens both features. The ST-IGA enables more accurate representation of the solid-surface geometries and increased accuracy in the flow solution in general. With the ST-IGA, even with just one quadratic NURBS element across the gap of the lubrication fluid dynamics problem, we reach a solution quality comparable to that of the Reynolds-equation model. The ST-SI enables moving-mesh computation when the spinning solid surface is noncircular. The mesh covering the solid surface spins with it, retaining the high-resolution representation of the flow near the surface, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. We present detailed 2D test computations to show how the method performs compared to the Reynolds-equation model, compared to finite element discretization, at different circumferential and normal mesh refinement levels, when there is an SI in the mesh, and when the no-slip boundary conditions are weakly-enforced.

    DOI

  • Methods for computation of flow-driven string dynamics in a pump and residence time

    Kanai, Taro, Takizawa, Kenji, Tezduyar, Tayfun E., Komiya, Kenji, Kaneko, Masayuki, Hirota, Kyohei, Nohmi, Motohiko, Tsuneda, Tomoki, Kawai, Masahito, Isono, Miho

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   29 ( 5 ) 839 - 870  2019年05月  [査読有り]

     概要を見る

    We present methods for computation of flow-driven string dynamics in a pump and related residence time. The string dynamics computations help us understand how the strings carried by a fluid interact with the pump surfaces, including the blades, and get stuck on or around those surfaces. The residence time computations help us to have a simplified but quick understanding of the string behavior. The core computational method is the Space-Time Variational Multiscale (ST-VMS) method, and the other key methods are the ST Isogeometric Analysis (ST-IGA), ST Slip Interface (ST-SI) method, ST/NURBS Mesh Update Method (STNMUM), a general-purpose NURBS mesh generation method for complex geometries, and a one-way-dependence model for the string dynamics. The ST-IGA with NURBS basis functions in space is used in both fluid mechanics and string structural dynamics. The ST framework provides higher-order accuracy. The VMS feature of the ST-VMS addresses the computational challenges associated with the turbulent nature of the unsteady flow, and the moving-mesh feature of the ST framework enables high-resolution computation near the rotor surface. The ST-SI enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA enables more accurate representation of the pump geometry and increased accuracy in the flow solution. The IGA discretization also enables increased accuracy in the structural dynamics solution, as well as smoothness in the string shape and fluid dynamics forces computed on the string. The STNMUM enables exact representation of the mesh rotation. The general-purpose NURBS mesh generation method makes it easier to deal with the complex geometry we have here. With the one-way-dependence model, we compute the influence of the flow on the string dynamics, while avoiding the formidable task of computing the influence of the string on the flow, which we expect to be small.

    DOI

  • Computational analysis methods for complex unsteady flow problems

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   29 ( 5 ) 825 - 838  2019年05月  [査読有り]

     概要を見る

    In this lead paper of the special issue, we provide a brief summary of the stabilized and multiscale methods in fluid dynamics. We highlight the key features of the stabilized and multiscale scale methods, and variational methods in general, that make these approaches well suited for computational analysis of complex, unsteady flows encountered in modern science and engineering applications. We mainly focus on the recent developments. We discuss application of the variational multiscale (VMS) methods to fluid dynamics problems involving computational challenges associated with high-Reynolds-number flows, wall-bounded turbulent flows, flows on moving domains including subdomains in relative motion, fluid-structure interaction (FSI), and complex-fluid flows with FSI.

    DOI

  • A stabilized ALE method for computational fluid-structure interaction analysis of passive morphing in turbomachinery

    Castorrini, Alessio, Corsini, Alessandro, Rispoli, Franco, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   29 ( 5 ) 967 - 994  2019年05月  [査読有り]

     概要を見る

    Computational fluid-structure interaction (FSI) and flow analysis now have a significant role in design and performance evaluation of turbomachinery systems, such as wind turbines, fans, and turbochargers. With increasing scope and fidelity, computational analysis can help improve the design and performance. For example, it can help add a passive morphing attachment (MA) to the blades of an axial fan for the purpose of controlling the blade load and section stall. We present a stabilized Arbitrary Lagrangian-Eulerian (ALE) method for computational FSI analysis of passive morphing in turbomachinery. The main components of the method are the Streamline-Upwind/Petrov-Galerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) stabilizations in the ALE framework, mesh moving with Jacobian-based stiffening, and block-iterative FSI coupling. The turbulent-flow nature of the analysis is handled with a Reynolds-Averaged Navier-Stokes (RANS) model and SUPG/PSPG stabilization, supplemented with the "DRDJ" stabilization. As the structure moves, the fluid mechanics mesh moves with the Jacobian-based stiffening method, which reduces the deformation of the smaller elements placed near the solid surfaces. The FSI coupling between the blocks of the fully-discretized equation system representing the fluid mechanics, structural mechanics, and mesh moving equations is handled with the block-iterative coupling method. We present two-dimensional (2D) and three-dimensional (3D) computational FSI studies for an MA added to an axial-fan blade. The results from the 2D study are used in determining the spanwise length of the MA in the 3D study.

    DOI

  • Space–time computations in practical engineering applications: a summary of the 25-year history

    Tezduyar T.E, Takizawa K

    Computational Mechanics   63 ( 4 ) 747 - 753  2019年04月  [査読有り]

    DOI

  • Isogeometric hyperelastic shell analysis with out-of-plane deformation mapping

    Takizawa, Kenji, Tezduyar, Tayfun E., Sasaki, Takafumi

    COMPUTATIONAL MECHANICS   63 ( 4 ) 681 - 700  2019年04月  [査読有り]

     概要を見る

    We derive a hyperelastic shell formulation based on the Kirchhoff-Love shell theory and isogeometric discretization, where we take into account the out-of-plane deformation mapping. Accounting for that mapping affects the curvature term. It also affects the accuracy in calculating the deformed-configuration out-of-plane position, and consequently the nonlinear response of the material. In fluid-structure interaction analysis, when the fluid is inside a shell structure, the shell midsurface is what it would know. We also propose, as an alternative, shifting the midsurface location in the shell analysis to the inner surface, which is the surface that the fluid should really see. Furthermore, in performing the integrations over the undeformed configuration, we take into account the curvature effects, and consequently integration volume does not change as we shift the midsurface location. We present test computations with pressurized cylindrical and spherical shells, with Neo-Hookean and Fung's models, for the compressible- and incompressible-material cases, and for two different locations of the midsurface. We also present test computation with a pressurized Y-shaped tube, intended to be a simplified artery model and serving as an example of cases with somewhat more complex geometry.

    DOI

  • Compressible-flow geometric-porosity modeling and spacecraft parachute computation with isogeometric discretization

    Kanai, Taro, Takizawa, Kenji, Tezduyar, Tayfun E., Tanaka, Tatsuya, Hartmann, Aaron

    COMPUTATIONAL MECHANICS   63 ( 2 ) 301 - 321  2019年02月  [査読有り]

     概要を見る

    One of the challenges in computational fluid-structure interaction (FSI) analysis of spacecraft parachutes is the geometric porosity, a design feature created by the hundreds of gaps and slits that the flow goes through. Because FSI analysis with resolved geometric porosity would be exceedingly time-consuming, accurate geometric-porosity modeling becomes essential. The geometric-porosity model introduced earlier in conjunction with the space-time FSI method enabled successful computational analysis and design studies of the Orion spacecraft parachutes in the incompressible-flow regime. Recently, porosity models and ST computational methods were introduced, in the context of finite element discretization, for compressible-flow aerodynamics of parachutes with geometric porosity. The key new component of the ST computational framework was the compressible-flow ST slip interface method, introduced in conjunction with the compressible-flow ST SUPG method. Here, we integrate these porosity models and ST computational methods with isogeometric discretization. We use quadratic NURBS basis functions in the computations reported. This gives us a parachute shape that is smoother than what we get from a typical finite element discretization. In the flow analysis, the combination of the ST framework, NURBS basis functions, and the SUPG stabilization assures superior computational accuracy. The computations we present for a drogue parachute show the effectiveness of the porosity models, ST computational methods, and the integration with isogeometric discretization.

    DOI

  • Turbocharger turbine and exhaust manifold flow computation with the Space–Time Variational Multiscale Method and Isogeometric Analysis

    Otoguro Y, Takizawa K, Tezduyar T.E, Nagaoka K, Mei S

    Computers and Fluids   179   764 - 776  2019年  [査読有り]

    DOI

  • Mesh refinement influence and cardiac-cycle flow periodicity in aorta flow analysis with isogeometric discretization

    Takizawa K, Tezduyar T.E, Uchikawa H, Terahara T, Sasaki T, Yoshida A

    Computers and Fluids   179   790 - 798  2019年  [査読有り]

    DOI

  • Computational analysis of flow-driven string dynamics in a pump and residence time calculation

    Komiya K, Kanai T, Otoguro Y, Kaneko M, Hirota K, Zhang Y, Takizawa K, Tezduyar T.E, Nohmi M, Tsuneda T, Kawai M, Isono M

    IOP Conference Series: Earth and Environmental Science   240 ( 6 )  2019年  [査読有り]

    DOI

  • Stabilization and discontinuity-capturing parameters for space–time flow computations with finite element and isogeometric discretizations

    Takizawa K, Tezduyar T.E, Otoguro Y

    Computational Mechanics   62 ( 5 ) 1169 - 1186  2018年11月  [査読有り]

    DOI

  • Space–Time computational analysis of tire aerodynamics with actual geometry, road contact, and tire deformation

    Kuraishi T, Takizawa K, Tezduyar T.E

    Modeling and Simulation in Science, Engineering and Technology     337 - 376  2018年  [査読有り]

    DOI

  • Recent advances in ALE-VMS and ST-VMS computational aerodynamic and FSI analysis of wind turbines

    Korobenko A, Bazilevs Y, Takizawa K, Tezduyar T.E

    Modeling and Simulation in Science, Engineering and Technology     253 - 336  2018年  [査読有り]

    DOI

  • Preface

    Tezduyar T.E

    Modeling and Simulation in Science, Engineering and Technology     vii - viii  2018年  [査読有り]

  • Heart valve flow computation with the space-time slip interface topology change (ST-SI-TC) method and isogeometric analysis (IGA)

    Kenji Takizawa, Tayfun E. Tezduyar, Takuya Terahara, Takafumi Sasaki

    Lecture Notes in Applied and Computational Mechanics   84   77 - 99  2018年  [査読有り]

     概要を見る

    We present a heart valve flow computation with the Space-Time Slip Interface Topology Change (ST-SI-TC) method and Isogeometric Analysis (IGA). The computation is for a realistic heart valve model with actual contact between the valve leaflets. The ST-SI-TC method integrates the ST-SI and ST-TC methods in the framework of the ST Variational Multiscale (ST-VMS) method. The STVMS method functions as a moving-mesh method, which maintains high-resolution boundary layer representation near the solid surfaces. The ST-TC method was introduced for moving-mesh computation of flow problems with TC, such as contact between the leaflets of a heart valve. It deals with the contact while maintaining highresolution representation near the leaflet surfaces. The ST-SI method was originally introduced to addresses the challenge involved in high-resolution representation of the boundary layers near spinning solid surfaces. The mesh covering a spinning solid surface spins with it, and the SI between that mesh and the rest of the mesh accurately connects the two sides. This maintains the high-resolution representation near solid surfaces. In the context of heart valves, the SI connects the sectors of meshes containing the leaflets, enabling a more effective mesh moving. In that context, the ST-SI-TC method enables high-resolution representation even when the contact is between leaflets that are covered by meshes with SI. It also enables dealing with contact location change or contact and sliding on the SI. With IGA, in addition to having a more accurate representation of the surfaces and increased accuracy in the flow solution, the element density in the narrow spaces near the contact areas is kept at a reasonable level. Furthermore, because the flow representation in the contact area has a wider support in IGA, the flow computation method becomes more robust. The computation we present for an aortic-valve model shows the effectiveness of the ST-SI-TC-IGA method.

    DOI

  • Estimation of element-based zero-stress state in arterial FSI computations with isogeometric wall discretization

    Kenji Takizawa, Tayfun E. Tezduyar, Takafumi Sasaki

    Lecture Notes in Applied and Computational Mechanics   84   101 - 122  2018年  [査読有り]

     概要を見る

    In patient-specific arterial fluid-structure interaction computations the image-based arterial geometry does not come from a zero-stress state (ZSS), requiring an estimation of the ZSS. A method for estimation of element-based ZSS (EBZSS) was introduced earlier in the context of finite element wall discretization. The method has three main components. 1. An iterative method, which starts with a calculated initial guess, is used for computing the EBZSS such that when a given pressure load is applied, the image-based target shape is matched. 2. A method for straight-tube segments is used for computing the EBZSS so that we match the given diameter and longitudinal stretch in the target configuration and the “opening angle.” 3. An element-based mapping between the artery and straight-tube is extracted from the mapping between the artery and straight-tube segments. This provides the mapping from the arterial configuration to the straight-tube configuration, and from the estimated EBZSS of the straight-tube configuration back to the arterial configuration, to be used as the initial guess for the iterative method that matches the image-based target shape. Here we introduce the version of the EBZSS estimation method with isogeometric wall discretization. With NURBS basis functions, we may be able to use larger elements, consequently less number of elements, compared to linear basis functions. Higher-order NURBS basis functions allow representation of more complex shapes within an element. To show how the new EBZSS estimation method performs, we present 2D test computations with straight-tube configurations.

    DOI

  • Comment on “Experimental investigation of Taylor vortex photocatalytic reactor for water purification”

    Mittal S, Tezduyar T.E

    Chemical Engineering Science   192   1262  2018年  [査読有り]

    DOI

  • Aorta flow analysis and heart valve flow and structure analysis

    Takizawa K, Tezduyar T.E, Uchikawa H, Terahara T, Sasaki T, Shiozaki K, Yoshida A, Komiya K, Inoue G

    Modeling and Simulation in Science, Engineering and Technology     29 - 89  2018年  [査読有り]

    DOI

  • A general-purpose NURBS mesh generation method for complex geometries

    Otoguro Y, Takizawa K, Tezduyar T.E

    Modeling and Simulation in Science, Engineering and Technology     399 - 434  2018年  [査読有り]

    DOI

  • Space–time VMS computational flow analysis with isogeometric discretization and a general-purpose NURBS mesh generation method

    Otoguro Y, Takizawa K, Tezduyar T.E

    Computers and Fluids   158   189 - 200  2017年11月  [査読有り]

    DOI

  • Heart valve flow computation with the integrated Space–Time VMS, Slip Interface, Topology Change and Isogeometric Discretization methods

    Takizawa K, Tezduyar T.E, Terahara T, Sasaki T

    Computers and Fluids   158   176 - 188  2017年11月  [査読有り]

    DOI

  • Porosity models and computational methods for compressible-flow aerodynamics of parachutes with geometric porosity

    Takizawa, Kenji, Tezduyar, Tayfun E., Kanai, Taro

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   27 ( 4 ) 771 - 806  2017年04月  [査読有り]

     概要を見る

    Spacecraft-parachute designs quite often include "geometric porosity" created by the hundreds of gaps and slits that the flow goes through. Computational fluid-structure interaction (FSI) analysis of these parachutes with resolved geometric porosity would be exceedingly challenging, and therefore accurate modeling of the geometric porosity is essential for reliable FSI analysis. The space-time FSI (STFSI) method with the homogenized modeling of geometric porosity has proven to be reliable in computational analysis and design studies of Orion spacecraft parachutes in the incompressible-flow regime. Here we introduce porosity models and ST computational methods for compressible-flow aerodynamics of parachutes with geometric porosity. The main components of the ST computational framework we use are the compressible-flow ST SUPG method, which was introduced earlier, and the compressible-flow ST Slip Interface method, which we introduce here. The computations we present for a drogue parachute show the effectiveness of the porosity models and ST computational methods.

    DOI

  • Turbocharger flow computations with the Space–Time Isogeometric Analysis (ST-IGA)

    Takizawa K, Tezduyar T.E, Otoguro Y, Terahara T, Kuraishi T, Hattori H

    Computers and Fluids   142   15 - 20  2017年01月  [査読有り]

    DOI

  • Computational analysis of flow-driven string dynamics in turbomachinery

    Takizawa, Kenji, Tezduyar, Tayfun E., Hattori, Hitoshi

    COMPUTERS & FLUIDS   142   109 - 117  2017年01月  [査読有り]

     概要を見る

    We focus on computational analysis of flow-driven string dynamics. The objective is to understand how the strings carried by a fluid interact with the solid surfaces present and get stuck on or around those surfaces. Our target application is turbomachinery, such as understanding how strings get stuck on or around the blades of a fan. The components of the method we developed for this purpose are the Space-Time Variational Multiscale (ST-VMS) and ST Slip Interface (ST-SI) methods for the fluid dynamics, and a one-way-dependence model and the Isogeometric Analysis (IGA) for the string dynamics. The ST-VMS method is the core computational technology and it also has the features of a turbulence model. The ST-SI method allows in a consistent fashion slip at the interface between the mesh covering a spinning solid surface and the mesh covering the rest of the domain, and with this, we maintain high-resolution representation of the boundary layers near spinning solid surfaces such as fan blades. With the one-way-dependence model, we compute the influence of the flow on the string dynamics, while avoiding the formidable task of computing the influence of the string on the flow, which we expect to be small. The IGA for the string dynamics gives us not only a higher-order method and smoothness in the structure shape, but also smoothness in the fluid dynamics forces calculated on the string. To demonstrate how the method can be used in computational analysis of flow-driven string dynamics, we present the pilot computations we carried out, for a duct with cylindrical obstacles and for a ventilating fan. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Space-Time method for flow computations with slip interfaces and topology changes (ST-SI-TC)

    Takizawa, Kenji, Tezduyar, Tayfun E., Asada, Shohei, Kuraishi, Takashi

    COMPUTERS & FLUIDS   141   124 - 134  2016年12月  [査読有り]

     概要を見る

    The Space-Time Variational Multiscale(ST-VMS) method was introduced to function as a moving-mesh method. It is the VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method. It has reasonably good turbulence modeling features and serves as a core computational method. The ST Slip Interface (ST-SI) method was introduced to addresses the challenge involved in high-resolution representation of the boundary layers near spinning solid surfaces. The mesh covering a spinning solid surface spins with it and thus maintains the high-resolution representation near it. The ST-TC method was introduced for moving-mesh computation of flow problems with topology changes, such as contact between solid surfaces. It deals with the TC while maintaining high-resolution boundary layer representation near solid surfaces. The "ST-SI-TC" method we introduce here integrates the ST-SI and ST-TC methods in the ST-VMS framework. It enables accurate flow analysis when we have a spinning solid surface that is in contact with a solid surface. We present two test computations with the ST-SI-TC method, and they are both with models of flow around a rotating tire with road contact and prescribed deformation, one with a 2D model, and one with a 3D model. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Ram-air parachute structural and fluid mechanics computations with the Space-Time Isogeometric Analysis (ST-IGA)

    Takizawa, Kenji, Tezduyar, Tayfun E., Terahara, Takuya

    COMPUTERS & FLUIDS   141   191 - 200  2016年12月  [査読有り]

     概要を見る

    We present a method for structural and fluid mechanics computations of ram-air parachutes. A ram-air parachute is a parafoil inflated by the airflow through the inlets at the leading edge. It has better control and gliding capability than round parachutes. Reliable analysis of ram-air parachutes requires accurate representation of the parafoil geometry, fabric porosity and the complex, multiscale flow behavior involved in this class of problems. The key components of the method are (i) the Space-Time Variational Multiscale (ST-VMS) method, (ii) the version of the ST Slip Interface (ST-SI) method where the SI is between a thin porous structure and the fluid on its two sides, (iii) the ST Isogeometric Analysis (ST-IGA), and (iv) special-purpose NURBS mesh generation techniques for the parachute structure and the flow field inside and outside the parafoil. The ST-VMS method is a stabilized formulation that also serves as a turbulence model and can deal effectively with the complex, multiscale flow behavior. With the STSI version for porosity modeling, we deal with the fabric porosity in a fashion consistent with how we deal with the standard SIs and how we enforce the Dirichlet boundary conditions weakly. The ST-IGA, with NURBS basis functions in space, gives us, with relatively few number of unknowns, accurate representation of the parafoil geometry and increased accuracy in the flow solution. The special-purpose mesh generation techniques enable NURBS representation of the structure and fluid domains with significant geometric complexity. The test computations we present are for building a starting parachute shape and a starting flow field associated with that parachute shape, which are the first two key steps in fluid-structure interaction analysis. The computations demonstrate the effectiveness of the method in this class of problems. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Flow analysis of a wave-energy air turbine with the SUPG/PSPG stabilization and Discontinuity-Capturing Directional Dissipation

    Lucio Cardillo, Alessandro Corsini, Giovanni Delibra, Franco Rispoli, Tayfun E. Tezduyar

    COMPUTERS & FLUIDS   141   184 - 190  2016年12月  [査読有り]

     概要を見る

    We present a flow analysis of a wave-energy air turbine, commonly known as Wells turbine. The focus here is on the computational method used in the analysis, based on the Streamline-Upwind/PetrovGalerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) stabilizations and the Discontinuity Capturing Directional Dissipation (DCDD). The SUPG/PSPG stabilization is used rather widely and successfully. The DCDD, first introduced to complement the SUPG/PSPG method in computations of incompressible flows in the presence of sharp solution gradients, was also shown to perform well in standard turbulent-flow test computations when compared to the Smagorinsky Large Eddy Simulation (LES) model. The results obtained in our computational analysis of the Wells turbine here compare favorably to the available experimental data, and this demonstrates that the DCDD method performs well also in turbomachinery flows. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Computational analysis of wind-turbine blade rain erosion

    Castorrini, Alessio, Corsini, Alessandro, Rispoli, Franco, Venturini, Paolo, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTERS & FLUIDS   141   175 - 183  2016年12月  [査読有り]

     概要を見る

    Wind-turbine blade rain erosion damage could be significant if the blades are not protected. This damage would not typically influence the structural integrity of the blades, but it could degrade the aerodynamic performance and therefore the power production. We present computational analysis of rain erosion in wind-turbine blades. The main components of the method used in the analysis are the Streamline-Upwind/Petrov-Galerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) stabilizations, a finite element particle-cloud tracking method, and an erosion model. The turbulent-flow nature of the analysis is handled with a RANS model and SUPG/PSPG stabilization, the particle-cloud trajectories are calculated based on the computed flow field and closure models defined for the turbulent dispersion of particles, and one-way dependence is assumed between the flow and particle dynamics. The erosion patterns are then computed based on the particle-cloud data. The patterns are consistent with those observed in the actual wind turbines. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Computational thermo-fluid analysis of a disk brake

    Takizawa, Kenji, Tezduyar, Tayfun E., Kuraishi, Takashi, Tabata, Shinichiro, Takagi, Hirokazu

    COMPUTATIONAL MECHANICS   57 ( 6 ) 965 - 977  2016年06月  [査読有り]

     概要を見る

    We present computational thermo-fluid analysis of a disk brake, including thermo-fluid analysis of the flow around the brake and heat conduction analysis of the disk. The computational challenges include proper representation of the small-scale thermo-fluid behavior, high-resolution representation of the thermo-fluid boundary layers near the spinning solid surfaces, and bringing the heat transfer coefficient (HTC) calculated in the thermo-fluid analysis of the flow to the heat conduction analysis of the spinning disk. The disk brake model used in the analysis closely represents the actual configuration, and this adds to the computational challenges. The components of the method we have developed for computational analysis of the class of problems with these types of challenges include the Space-Time Variational Multiscale method for coupled incompressible flow and thermal transport, ST Slip Interface method for high-resolution representation of the thermo-fluid boundary layers near spinning solid surfaces, and a set of projection methods for different parts of the disk to bring the HTC calculated in the thermo-fluid analysis. With the HTC coming from the thermo-fluid analysis of the flow around the brake, we do the heat conduction analysis of the disk, from the start of the breaking until the disk spinning stops, demonstrating how the method developed works in computational analysis of this complex and challenging problem.

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  • SUPG/PSPG computational analysis of rain erosion in wind-turbine blades

    Alessio Castorrini, Alessandro Corsini, Franco Rispoli, Paolo Venturini, Kenji Takizawa, Tayfun E. Tezduyar

    Modeling and Simulation in Science, Engineering and Technology     77 - 96  2016年  [査読有り]

     概要を見る

    Wind-turbine blades exposed to rain can be damaged by erosion if not protected. Although this damage does not typically influence the structural response of the blades,it could heavily degrade the aerodynamic performance,and therefore the power production. We present a method for computational analysis of rain erosion in wind-turbine blades. The method is based on a stabilized finite element fluid mechanics formulation and a finite element particle-cloud tracking method. Accurate representation of the flow would be essential in reliable computational turbomachinery analysis and design. The turbulent-flow nature of the problem is dealt with a RANS model and SUPG/PSPG stabilization,the particle-cloud trajectories are calculated based on the flow field and closure models for the turbulence-particle interaction,and one-way dependence is assumed between the flow field and particle dynamics. The erosion patterns are then computed based on the particle-cloud data.

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  • New directions in space-time computational methods

    Kenji Takizawa, Tayfun E. Tezduyar

    Modeling and Simulation in Science, Engineering and Technology     159 - 178  2016年  [査読有り]

     概要を見る

    This is an overview of some of the new directions we have taken the space-time (ST) computational methods since 2010 in bringing solution and analysis to different classes of challenging engineering problems. The new directions include the variational multiscale (VMS) version of the Deforming-Spatial-Domain/Stabilized ST method,using NURBS basis functions in temporal representation of the unknown variables and motion of the solid surfaces and fluid mechanics meshes,ST techniques with continuous representation in time,ST interface-tracking with topology change,and the ST-VMS method for flow computations with slip interfaces. We describe these new directions and present a few examples.

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  • Flow analysis of a wave-energy air turbine with the SUPG/PSPG method and DCDD

    Cardillo L, Corsini A, Delibra G, Rispoli F, Tezduyar T.E

    Modeling and Simulation in Science, Engineering and Technology     39 - 53  2016年  [査読有り]

    DOI

  • Aorta modeling with the element-based zero-stress state and isogeometric discretization

    Takizawa K, Tezduyar T.E, Sasaki T

    Computational Mechanics   59 ( 2 ) 1 - 16  2016年  [査読有り]

    DOI

  • A geometrical-characteristics study in patient-specific FSI analysis of blood flow in the thoracic aorta

    Hiroshi Suito, Kenji Takizawa, Viet Q. H. Huynh, Daniel Sze, Takuya Ueda, Tayfun E. Tezduyar

    Modeling and Simulation in Science, Engineering and Technology     379 - 386  2016年  [査読有り]

     概要を見る

    This chapter is on fluid-structure interaction (FSI) analysis of blood flow in the thoracic aorta. The FSI is handled with the Sequentially Coupled Arterial FSI technique. We focus on the relationship between the aorta centerline geometry and the wall shear stress (WSS) distribution. The model centerlines are extracted from the CT scans,and we assume a constant diameter for the artery segment. Then,torsion-free model geometries are generated by projecting the original centerline to its averaged plane of curvature. The WSS distributions for the original and projected geometries are compared to examine the influence of the torsion.

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  • Space-time VMS method for flow computations with slip interfaces (ST-SI)

    Takizawa, Kenji, Tezduyar, Tayfun E., Mochizuki, Hiroki, Hattori, Hitoshi, Mei, Sen, Pan, Linqi, Montel, Kenneth

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   25 ( 12 ) 2377 - 2406  2015年11月  [査読有り]

     概要を見る

    We present the space-time variational multiscale (ST-VMS) method for flow computations with slip interfaces (ST-SI). The method is intended for fluid-structure interaction (FSI) analysis where one or more of the subdomains contain spinning structures, such as the rotor of a wind turbine, and the subdomains are covered by meshes that do not match at the interface and have slip between them. The mesh covering a subdomain with the spinning structure spins with it, thus maintaining the high-resolution representation of the boundary layers near the structure. The starting point in the development of the method is the version of the arbitrary Lagrangian-Eulerian VMS (ALE-VMS) method designed for computations with "sliding interfaces". Interface terms similar to those in the ALE-VMS version are added to the ST-VMS formulation to account for the compatibility conditions for the velocity and stress. In addition to having a high-resolution representation of the boundary layers, because the ST framework allows NURBS functions in temporal representation of the structure motion, we have exact representation of the circular paths associated with the spinning. The ST-SI method includes versions for cases where the SI is between fluid and solid domains with weakly-imposed Dirichlet conditions for the fluid and for cases where the SI is between a thin porous structure and the fluid on its two sides. Test computations with 2D and 3D models of a vertical-axis wind turbine show the effectiveness of the ST-SI method.

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  • New directions and challenging computations in fluid dynamics modeling with stabilized and multiscale methods

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   25 ( 12 ) 2217 - 2226  2015年11月  [査読有り]

     概要を見る

    In this paper, we provide a brief overview of the development of stabilized and multiscale methods in fluid dynamics. We mainly focus on recent developments and new directions in the variational multiscale (VMS) methods. We also discuss applications of the VMS techniques to fluid dynamics problems involving computational challenges associated with high-Reynolds-number flows, wall-bounded turbulent flows, flows with moving domains including subdomains in relative motion, and free-surface flows.

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  • Multiscale space-time methods for thermo-fluid analysis of a ground vehicle and its tires

    Takizawa, Kenji, Tezduyar, Tayfun E., Kuraishi, Takashi

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   25 ( 12 ) 2227 - 2255  2015年11月  [査読有り]

     概要を見る

    We present the core and special multiscale space-time (ST) methods we developed for thermo-fluid analysis of a ground vehicle and its tires. We also present application of these methods to thermo-fluid analysis of a freight truck and its rear set of tires. The core multiscale ST method is the ST variational multiscale (ST-VMS) formulation of the Navier-Stokes equations of incompressible flows with thermal coupling, which is multiscale in the way the small-scale thermo-fluid behavior is represented in the computations. The special multiscale ST method is spatially multiscale, where the thermo-fluid computation over the global domain with a reasonable mesh refinement is followed by a higher-resolution computation over the local domain containing the rear set of tires, with the boundary and initial conditions coming from the data computed over the global domain. The large amount of time-history data from the global computation is stored using the ST computation technique with continuous representation in time (ST-C), which serves as a data compression technique in this context. In our thermo-fluid analysis, we use a road-surface temperature higher than the free-stream temperature, and a tire-surface temperature that is even higher. We also include in the analysis the heat from the engine and exhaust system, with a reasonably realistic representation of the rate by which that heat transfer takes place as well as the surface geometry of the engine and exhaust system over which the heat transfer occurs. We take into account the heave motion of the truck body. We demonstrate how the spatially multiscale ST method, with higher-refinement mesh in the local domain, substantially increases the accuracy of the computed heat transfer rates from the tires.

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  • Special methods for aerodynamic-moment calculations from parachute FSI modeling

    Takizawa, Kenji, Tezduyar, Tayfun E., Boswell, Cody, Tsutsui, Yuki, Montel, Kenneth

    COMPUTATIONAL MECHANICS   55 ( 6 ) 1059 - 1069  2015年06月  [査読有り]

     概要を見る

    The space-time fluid-structure interaction (STFSI) methods for 3D parachute modeling are now at a level where they can bring reliable, practical analysis to some of the most complex parachute systems, such as spacecraft parachutes. The methods include the Deforming-Spatial-Domain/Stabilized ST method as the core computational technology, and a good number of special FSI methods targeting parachutes. Evaluating the stability characteristics of a parachute based on how the aerodynamic moment varies as a function of the angle of attack is one of the practical analyses that reliable parachute FSI modeling can deliver. We describe the special FSI methods we developed for this specific purpose and present the aerodynamic-moment data obtained from FSI modeling of NASA Orion spacecraft parachutes and Japan Aerospace Exploration Agency (JAXA) subscale parachutes.

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  • Space-time computational analysis of MAV flapping-wing aerodynamics with wing clapping

    Takizawa, Kenji, Tezduyar, Tayfun E., Buscher, Austin

    COMPUTATIONAL MECHANICS   55 ( 6 ) 1131 - 1141  2015年06月  [査読有り]

     概要を見る

    Computational analysis of flapping-wing aerodynamics with wing clapping was one of the classes of computations targeted in introducing the space-time (ST) interface-tracking method with topology change (ST-TC). The ST-TC method is a new version of the deforming-spatial-domain/stabilized ST (DSD/SST) method, enhanced with a master-slave system that maintains the connectivity of the "parent" fluid mechanics mesh when there is contact between the moving interfaces. With that enhancement and because of its ST nature, the ST-TC method can deal with an actual contact between solid surfaces in flow problems with moving interfaces. It accomplishes that while still possessing the desirable features of interface-tracking (moving-mesh) methods, such as better resolution of the boundary layers. Earlier versions of the DSD/SST method, with effective mesh update, were already able to handle moving-interface problems when the solid surfaces are in near contact or create near TC. Flapping-wing aerodynamics of an actual locust, with the forewings and hindwings crossing each other very close and creating near TC, is an example of successfully computed problems. Flapping-wing aerodynamics of a micro aerial vehicle (MAV) with the wings of an actual locust is another example. Here we show how the ST-TC method enables 3D computational analysis of flapping-wing aerodynamics of an MAV with wing clapping. In the analysis, the wings are brought into an actual contact when they clap. We present results for a model dragonfly MAV.

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  • Particle tracking and particle-shock interaction in compressible-flow computations with the V-SGS stabilization and Y Z beta shock-capturing

    Franco Rispoli, Giovanni Delibra, Paolo Venturini, Alessandro Corsini, Rafael Saavedra, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   55 ( 6 ) 1201 - 1209  2015年06月  [査読有り]

     概要を見る

    The Y Z beta shock-capturing technique, which is residual-based, was introduced in conjunction with the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation of compressible flows in conservation variables. It was later also combined with the variable subgrid scale (V-SGS) formulation of compressible flows in conservation variables and successfully tested on 2D and 3D computation of inviscid flows with shocks. In this paper we extend that combined method to inviscid flow computations with particle tracking and particle-shock interaction. Particles are tracked individually, assuming one-way dependence between the particle dynamics and the flow. We present two steady-state test computations with particle-shock interaction, one in 2D and one in 3D, and show that the overall method is effective in particle tracking and particle-shock interaction analysis in compressible flows.

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  • FSI modeling of the Orion spacecraft drogue parachutes

    Takizawa, Kenji, Tezduyar, Tayfun E., Kolesar, Ryan

    COMPUTATIONAL MECHANICS   55 ( 6 ) 1167 - 1179  2015年06月  [査読有り]

     概要を見る

    The space-time fluid-structure interaction (STFSI) methods for parachute modeling are now capable of bringing reliable analysis to spacecraft parachutes, which pose formidable computational challenges. A number of special FSI methods targeting spacecraft parachutes complement the STFSI core computational technology in addressing these challenges. Until recently, these challenges were addressed for the Orion spacecraft main parachutes, which are the parachutes used for landing, and in the incompressible-flow regime, which is where the main parachutes operate. At higher altitudes the Orion spacecraft will rely on drogue parachutes. These parachutes have a ribbon construction, and in FSI modeling this creates geometric and flow complexities comparable to those encountered in FSI modeling of the main parachutes, which have a ringsail construction. Like the main parachutes, the drogue parachutes will be used in multiple stages-two reefed stages and a fully-open stage. A reefed stage is where a cable along the parachute skirt constrains the diameter to be less than the diameter in the subsequent stage. After a period of time during the descent at the reefed stage, the cable is cut and the parachute disreefs (i.e. expands) to the next stage. The reefed stages and disreefing involve computational challenges beyond those in FSI modeling of fully-open drogue parachutes. We present the special modeling techniques we devised to address the computational challenges and the results from the computations carried out. The flight envelope of the Orion drogue parachutes includes regions where the Mach number is high enough to require a compressible-flow solver. We present a preliminary fluid mechanics computation for such a case.

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  • Fluid-structure interaction

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   55 ( 6 ) 1057 - 1058  2015年06月  [査読有り]

    DOI

  • Multiscale space-time methods for thermo-fluid analysis of a ground vehicle and its tires

    Takizawa K, Tezduyar T.E, Kuraishi T

    Mathematical Models and Methods in Applied Sciences   25 ( 12 ) 2227 - 2255  2015年  [査読有り]

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  • Multiscale methods for gore curvature calculations from FSI modeling of spacecraft parachutes

    Takizawa, Kenji, Tezduyar, Tayfun E., Kolesar, Ryan, Boswell, Cody, Kanai, Taro, Montel, Kenneth

    COMPUTATIONAL MECHANICS   54 ( 6 ) 1461 - 1476  2014年12月  [査読有り]

     概要を見る

    There are now some sophisticated and powerful methods for computer modeling of parachutes. These methods are capable of addressing some of the most formidable computational challenges encountered in parachute modeling, including fluid-structure interaction (FSI) between the parachute and air flow, design complexities such as those seen in spacecraft parachutes, and operational complexities such as use in clusters and disreefing. One should be able to extract from a reliable full-scale parachute modeling any data or analysis needed. In some cases, however, the parachute engineers may want to perform quickly an extended or repetitive analysis with methods based on simplified models. Some of the data needed by a simplified model can very effectively be extracted from a full-scale computer modeling that serves as a pilot. A good example of such data is the circumferential curvature of a parachute gore, where a gore is the slice of the parachute canopy between two radial reinforcement cables running from the parachute vent to the skirt. We present the multiscale methods we devised for gore curvature calculation from FSI modeling of spacecraft parachutes. The methods include those based on the multiscale sequentially-coupled FSI technique and using NURBS meshes. We show how the methods work for the fully-open and two reefed stages of the Orion spacecraft main and drogue parachutes.

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  • Engineering Analysis and Design with ALE-VMS and Space-Time Methods

    Takizawa, Kenji, Bazilevs, Yuri, Tezduyar, Tayfun E., Hsu, Ming-Chen, Oiseth, Ole, Mathisen, Kjell M., Kostov, Nikolay, McIntyre, Spenser

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   21 ( 4 ) 481 - 508  2014年12月  [査読有り]

     概要を見る

    Flow problems with moving boundaries and interfaces include fluid-structure interaction (FSI) and a number of other classes of problems, have an important place in engineering analysis and design, and offer some formidable computational challenges. Bringing solution and analysis to them motivated the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) method and also the variational multiscale version of the Arbitrary Lagrangian-Eulerian method (ALE-VMS). Since their inception, these two methods and their improved versions have been applied to a diverse set of challenging problems with a common core computational technology need. The classes of problems solved include free-surface and two-fluid flows, fluid-object and fluid-particle interaction, FSI, and flows with solid surfaces in fast, linear or rotational relative motion. Some of the most challenging FSI problems, including parachute FSI, wind-turbine FSI and arterial FSI, are being solved and analyzed with the DSD/SST and ALE-VMS methods as core technologies. Better accuracy and improved turbulence modeling were brought with the recently-introduced VMS version of the DSD/SST method, which is called DSD/SST-VMST (also ST-VMS). In specific classes of problems, such as parachute FSI, arterial FSI, ship hydrodynamics, fluid-object interaction, aerodynamics of flapping wings, and wind-turbine aerodynamics and FSI, the scope and accuracy of the FSI modeling were increased with the special ALE-VMS and ST FSI techniques targeting each of those classes of problems. This article provides an overview of the core ALE-VMS and ST FSI techniques, their recent versions, and the special ALE-VMS and ST FSI techniques. It also provides examples of challenging problems solved and analyzed in parachute FSI, arterial FSI, ship hydrodynamics, aerodynamics of flapping wings, wind-turbine aerodynamics, and bridge-deck aerodynamics and vortex-induced vibrations.

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  • Aerodynamic and FSI Analysis of Wind Turbines with the ALE-VMS and ST-VMS Methods

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E., Hsu, Ming-Chen, Kostov, Nikolay, McIntyre, Spenser

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   21 ( 4 ) 359 - 398  2014年12月  [査読有り]

     概要を見る

    We provide an overview of the aerodynamic and FSI analysis of wind turbines the first three authors' teams carried out in recent years with the ALE-VMS and ST-VMS methods. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian-Eulerian (ALE) method. The VMS components are from the residual-based VMS (RBVMS) method. The ST-VMS method is the VMS version of the deforming-spatial-domain/stabilized space-time (DSD/SST) method. The techniques complementing these core methods include weak enforcement of the essential boundary conditions, NURBS-based isogeometric analysis, using NURBS basis functions in temporal representation of the rotor motion, mesh motion and also in remeshing, rotation representation with constant angular velocity, Kirchhoff-Love shell modeling of the rotor-blade structure, and full FSI coupling. The analysis cases include the aerodynamics of standalone wind-turbine rotors, wind-turbine rotor and tower, and the FSI that accounts for the deformation of the rotor blades. The specific wind turbines considered are NREL 5MW, NREL Phase VI and Micon 65/13M, all at full scale, and our analysis for NREL Phase VI and Micon 65/13M includes comparison with the experimental data.

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  • ST and ALE-VMS methods for patient-specific cardiovascular fluid mechanics modeling

    Takizawa, Kenji, Bazilevs, Yuri, Tezduyar, Tayfun E., Long, Christopher C., Marsden, Alison L., Schjodt, Kathleen

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   24 ( 12 ) 2437 - 2486  2014年11月  [査読有り]

     概要を見る

    This paper provides a review of the space-time (ST) and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the first three authors' research teams for patient-specific cardiovascular fluid mechanics modeling, including fluid-structure interaction (FSI). The core methods are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized ST formulation, and the stabilized ST FSI technique. A good number of special techniques targeting cardiovascular fluid mechanics have been developed to be used with the core methods. These include: (i) arterial-surface extraction and boundary condition techniques, (ii) techniques for using variable arterial wall thickness, (iii) methods for calculating an estimated zero-pressure arterial geometry, (iv) techniques for prestressing of the blood vessel wall, (v) mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, (vi) a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, (vii) a scaling technique for specifying a more realistic volumetric flow rate, (viii) techniques for the projection of fluid-structure interface stresses, (ix) a recipe for pre-FSI computations that improve the convergence of the FSI computations, (x) the Sequentially-Coupled Arterial FSI technique and its multiscale versions, (xi) techniques for calculation of the wall shear stress (WSS) and oscillatory shear index (OSI), (xii) methods for stent modeling and mesh generation, (xiii) methods for calculation of the particle residence time, and (xiv) methods for an estimated element-based zero-stress state for the artery. Here we provide an overview of the special techniques for WSS and OSI calculations, stent modeling and mesh generation, and calculation of the residence time with application to pulsatile ventricular assist device (PVAD). We provide references for some of the other special techniques. With results from earlier computations, we show how these core and special techniques work.

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  • FSI modeling of the reefed stages and disreefing of the Orion spacecraft parachutes

    Takizawa, Kenji, Tezduyar, Tayfun E., Boswell, Cody, Kolesar, Ryan, Montel, Kenneth

    COMPUTATIONAL MECHANICS   54 ( 5 ) 1203 - 1220  2014年11月  [査読有り]

     概要を見る

    Orion spacecraft main and drogue parachutes are used in multiple stages, starting with a "reefed" stage where a cable along the parachute skirt constrains the diameter to be less than the diameter in the subsequent stage. After a period of time during the descent, the cable is cut and the parachute "disreefs" (i.e. expands) to the next stage. Fluid-structure interaction (FSI) modeling of the reefed stages and disreefing involve computational challenges beyond those in FSI modeling of fully-open spacecraft parachutes. These additional challenges are created by the increased geometric complexities and by the rapid changes in the parachute geometry during disreefing. The computational challenges are further increased because of the added geometric porosity of the latest design of the Orion spacecraft main parachutes. The "windows" created by the removal of panels compound the geometric and flow complexity. That is because the Homogenized Modeling of Geometric Porosity, introduced to deal with the flow through the hundreds of gaps and slits involved in the construction of spacecraft parachutes, cannot accurately model the flow through the windows, which needs to be actually resolved during the FSI computation. In parachute FSI computations, the resolved geometric porosity is significantly more challenging than the modeled geometric porosity, especially in computing the reefed stages and disreefing. Orion spacecraft main and drogue parachutes will both have three stages, with computation of the Stage 1 shape and disreefing from Stage 1 to Stage 2 for the main parachute being the most challenging because of the lowest "reefing ratio" (the ratio of the reefed skirt diameter to the nominal diameter). We present the special modeling techniques and strategies we devised to address the computational challenges encountered in FSI modeling of the reefed stages and disreefing of the main and drogue parachutes. We report, for a single parachute, FSI computation of both reefed stages and both disreefing events for both the main and drogue parachutes. In the case of the main parachute, we also report, for a 2-parachute cluster, FSI computation of the disreefing from Stage 2 to Stage 3. With results from these computations, we demonstrate that we have to a great extent overcome one of the most formidable challenges in FSI modeling of spacecraft parachutes.

    DOI

  • A variational multiscale method for particle-cloud tracking in turbomachinery flows

    A. Corsini, F. Rispoli, A. G. Sheard, K. Takizawa, T. E. Tezduyar, P. Venturini

    COMPUTATIONAL MECHANICS   54 ( 5 ) 1191 - 1202  2014年11月  [査読有り]

     概要を見る

    We present a computational method for simulation of particle-laden flows in turbomachinery. The method is based on a stabilized finite element fluid mechanics formulation and a finite element particle-cloud tracking method. We focus on induced-draft fans used in process industries to extract exhaust gases in the form of a two-phase fluid with a dispersed solid phase. The particle-laden flow causes material wear on the fan blades, degrading their aerodynamic performance, and therefore accurate simulation of the flow would be essential in reliable computational turbomachinery analysis and design. The turbulent-flow nature of the problem is dealt with a Reynolds-Averaged Navier-Stokes model and Streamline-Upwind/Petrov-Galerkin/Pressure-Stabilizing/Petrov-Galerkin stabilization, the particle-cloud trajectories are calculated based on the flow field and closure models for the turbulence-particle interaction, and one-way dependence is assumed between the flow field and particle dynamics. We propose a closure model utilizing the scale separation feature of the variational multiscale method, and compare that to the closure utilizing the eddy viscosity model. We present computations for axial- and centrifugal-fan configurations, and compare the computed data to those obtained from experiments, analytical approaches, and other computational methods.

    DOI

  • Space-time interface-tracking with topology change (ST-TC)

    Takizawa, Kenji, Tezduyar, Tayfun E., Buscher, Austin, Asada, Shohei

    COMPUTATIONAL MECHANICS   54 ( 4 ) 955 - 971  2014年10月  [査読有り]

     概要を見る

    To address the computational challenges associated with contact between moving interfaces, such as those in cardiovascular fluid-structure interaction (FSI), parachute FSI, and flapping-wing aerodynamics, we introduce a space-time (ST) interface-tracking method that can deal with topology change (TC). In cardiovascular FSI, our primary target is heart valves. The method is a new version of the deforming-spatial-domain/stabilized space-time (DSD/SST) method, and we call it ST-TC. It includes a master-slave system that maintains the connectivity of the "parent" mesh when there is contact between the moving interfaces. It is an efficient, practical alternative to using unstructured ST meshes, but without giving up on the accurate representation of the interface or consistent representation of the interface motion. We explain the method with conceptual examples and present 2D test computations with models representative of the classes of problems we are targeting.

    DOI

  • Space-time fluid mechanics computation of heart valve models

    Takizawa, Kenji, Tezduyar, Tayfun E., Buscher, Austin, Asada, Shohei

    COMPUTATIONAL MECHANICS   54 ( 4 ) 973 - 986  2014年10月  [査読有り]

     概要を見る

    Fluid mechanics computation of heart valves with an interface-tracking (moving-mesh) method was one of the classes of computations targeted in introducing the space-time (ST) interface tracking method with topology change (ST-TC). The ST-TC method is a new version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method. It can deal with an actual contact between solid surfaces in flow problems with moving interfaces, while still possessing the desirable features of interface-tracking methods, such as better resolution of the boundary layers. The DSD/SST method with effective mesh update can already handle moving-interface problems when the solid surfaces are in near contact or create near TC, if the "nearness" is sufficiently "near" for the purpose of solving the problem. That, however, is not the case in fluid mechanics of heart valves, as the solid surfaces need to be brought into an actual contact when the flow has to be completely blocked. Here we extend the ST-TC method to 3D fluid mechanics computation of heart valve models. We present computations for two models: an aortic valve with coronary arteries and a mechanical aortic valve. These computations demonstrate that the ST-TC method can bring interface-tracking accuracy to fluid mechanics of heart valves, and can do that with computational practicality.

    DOI

  • Estimation of element-based zero-stress state for arterial FSI computations

    Takizawa, Kenji, Takagi, Hirokazu, Tezduyar, Tayfun E., Torii, Ryo

    COMPUTATIONAL MECHANICS   54 ( 4 ) 895 - 910  2014年10月  [査読有り]

     概要を見る

    In patient-specific arterial fluid-structure interaction (FSI) computations the image-based arterial geometry comes from a configuration that is not stress-free. We present a method for estimation of element-based zero-stress (ZS) state. The method has three main components. (1) An iterative method, which starts with an initial guess for the ZS state, is used for computing the element-based ZS state such that when a given pressure load is applied, the image-based target shape is matched. (2) A method for straight-tube geometries with single and multiple layers is used for computing the element-based ZS state so that we match the given diameter and longitudinal stretch in the target configuration and the "opening angle." (3) An element-based mapping between the arterial and straight-tube configurations is used for mapping from the arterial configuration to the straight-tube configuration, and for mapping the estimated ZS state of the straight tube back to the arterial configuration, to be used as the initial guess for the iterative method that matches the image-based target shape. We present a set of test computations to show how the method works.

    DOI

  • Coronary arterial dynamics computation with medical-image-based time-dependent anatomical models and element-based zero-stress state estimates

    Takizawa, Kenji, Torii, Ryo, Takagi, Hirokazu, Tezduyar, Tayfun E., Xu, Xiao Y.

    COMPUTATIONAL MECHANICS   54 ( 4 ) 1047 - 1053  2014年10月  [査読有り]

     概要を見る

    We propose a method for coronary arterial dynamics computation with medical-image-based time-dependent anatomical models. The objective is to improve the computational analysis of coronary arteries for better understanding of the links between the atherosclerosis development and mechanical stimuli such as endothelial wall shear stress and structural stress in the arterial wall. The method has two components. The first one is element-based zero-stress (ZS) state estimation, which is an alternative to prestress calculation. The second one is a "mixed ZS state" approach, where the ZS states for different elements in the structural mechanics mesh are estimated with reference configurations based on medical images coming from different instants within the cardiac cycle. We demonstrate the robustness of the method in a patient-specific coronary arterial dynamics computation where the motion of a thin strip along the arterial surface and two cut surfaces at the arterial ends is specified to match the motion extracted from the medical images.

    DOI

  • Biomedical fluid mechanics and fluid-structure interaction

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   54 ( 4 ) 893 - 893  2014年10月  [査読有り]

    DOI

  • Sequentially-coupled space-time FSI analysis of bio-inspired flapping-wing aerodynamics of an MAV

    Takizawa, Kenji, Tezduyar, Tayfun E., Kostov, Nikolay

    COMPUTATIONAL MECHANICS   54 ( 2 ) 213 - 233  2014年08月  [査読有り]

     概要を見る

    We present a sequentially-coupled space-time (ST) computational fluid-structure interaction (FSI) analysis of flapping-wing aerodynamics of a micro aerial vehicle (MAV). The wing motion and deformation data, whether prescribed fully or partially, is from an actual locust, extracted from high-speed, multi-camera video recordings of the locust in a wind tunnel. The core computational FSI technology is based on the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) formulation. This is supplemented with using NURBS basis functions in temporal representation of the wing and mesh motion, and in remeshing. Here we use the version of the DSD/SST formulation derived in conjunction with the variational multiscale (VMS) method, and this version is called "DSD/SST-VMST." The structural mechanics computations are based on the Kirchhoff-Love shell model. The sequential-coupling technique is applicable to some classes of FSI problems, especially those with temporally-periodic behavior. We show that it performs well in FSI computations of the flapping-wing aerodynamics we consider here. In addition to the straight-flight case, we analyze cases where the MAV body has rolling, pitching, or rolling and pitching motion. We study how all these influence the lift and thrust.

    DOI

  • Space-time computation techniques with continuous representation in time (ST-C)

    Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   53 ( 1 ) 91 - 99  2014年01月  [査読有り]

     概要を見る

    We introduce space-time computation techniques with continuous representation in time (ST-C), using temporal NURBS basis functions. This gives us a temporally smooth, NURBS-based solution, which is desirable in some cases, and a more efficient way of dealing with the computed data. We propose two versions of ST-C. In the first version, the smooth solution is extracted by projection from a solution computed with a different temporal representation, typically a discontinuous one. We use a successive projection technique with a small number of temporal NURBS basis functions at each projection, and therefore the extraction can take place as the solution with discontinuous temporal representation is being computed, without storing a large amount of time-history data. This version is not limited to solutions computed with ST techniques. In the second version, the solution with continuous temporal representation is computed directly by using a small number of temporal NURBS basis functions in the variational formulation associated with each time step.

    DOI

  • Space-time VMS computation of wind-turbine rotor and tower aerodynamics

    Takizawa, Kenji, Tezduyar, Tayfun E., McIntyre, Spenser, Kostov, Nikolay, Kolesar, Ryan, Habluetzel, Casey

    COMPUTATIONAL MECHANICS   53 ( 1 ) 1 - 15  2014年01月  [査読有り]

     概要を見る

    We present the space-time variational multiscale (ST-VMS) computation of wind-turbine rotor and tower aerodynamics. The rotor geometry is that of the NREL 5MW offshore baseline wind turbine. We compute with a given wind speed and a specified rotor speed. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. The presence of the tower increases the computational challenge because of the fast, rotational relative motion between the rotor and tower. The ST-VMS method is the residual-based VMS version of the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) method, and is also called "DSD/SST-VMST" method (i.e., the version with the VMS turbulence model). In calculating the stabilization parameters embedded in the method, we are using a new element length definition for the diffusion-dominated limit. The DSD/SST method, which was introduced as a general-purpose moving-mesh method for computation of flows with moving interfaces, requires a mesh update method. Mesh update typically consists of moving the mesh for as long as possible and remeshing as needed. In the computations reported here, NURBS basis functions are used for the temporal representation of the rotor motion, enabling us to represent the circular paths associated with that motion exactly and specify a constant angular velocity corresponding to the invariant speeds along those paths. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. We name this "ST/NURBS Mesh Update Method (STNMUM)." The STNMUM increases computational efficiency in terms of computer time and storage, and computational flexibility in terms of being able to change the time-step size of the computation. We use layers of thin elements near the blade surfaces, which undergo rigid-body motion with the rotor. We compare the results from computations with and without tower, and we also compare using NURBS and linear finite element basis functions in temporal representation of the mesh motion.

    DOI

  • Patient-specific cardiovascular fluid mechanics analysis with the ST and ALE-VMS methods

    Kenji Takizawa, Yuri Bazilevs, Tayfun E. Tezduyar, Christopher C. Long, Alison L. Marsden, Kathleen Schjodt

    Computational Methods in Applied Sciences   33   71 - 102  2014年  [査読有り]

     概要を見る

    This chapter provides an overview of how patient-specific cardiovascular fluid mechanics analysis, including fluid-structure interaction (FSI), can be carried out with the space-time (ST) and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the first three authors' research teams. The core methods are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized ST formulation, and the stabilized ST FSI technique. A good number of special techniques targeting cardiovascular fluid mechanics have been developed to be used with the coremethods. These include (i) arterial-surface extraction and boundary condition techniques, (ii) techniques for using variable arterialwall thickness, (iii) methods for calculating an estimated zero-pressure arterial geometry, (iv) techniques for prestressing of the blood vessel wall, (v) mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, (vi) a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, (vii) a scaling technique for specifying a more realistic volumetric flow rate, (viii) techniques for the projection of fluid-structure interface stresses, (ix) a recipe for pre-FSI computations that improve the convergence of the FSI computations, (x) the Sequentially-Coupled Arterial FSI technique and its multiscale versions, (xi) techniques for calculation of the wall shear stress (WSS) and oscillatory shear index (OSI), (xii) methods for stent modeling and mesh generation, (xiii) methods for calculation of the particle residence time, and (xiv) methods for an estimated element-based zero-stress state for the artery. Here we provide an overview of the special techniques for stent modeling and mesh generation and calculation of the residence time with application to pulsatile ventricular assist device (PVAD). We provide references for some of the other special techniques. With results from earlier computations, we show how the core and special techniques work.

    DOI

  • Fluid–structure interaction modeling of patient-specific cerebral aneurysms

    Takizawa K, Tezduyar T.E

    Lecture Notes in Computational Vision and Biomechanics   12   25 - 45  2014年  [査読有り]

    DOI

  • Computational engineering analysis and design with ALE-VMS and ST methods

    Kenji Takizawa, Yuri Bazilevs, Tayfun E. Tezduyar, Ming-Chen Hsu, Ole Øiseth, Kjell M. Mathisen, Nikolay Kostov, Spenser McIntyre

    Computational Methods in Applied Sciences   33   321 - 353  2014年  [査読有り]

     概要を見る

    Flows with moving interfaces include fluid-structure interaction (FSI) and quite a few other classes of problems, have an important place in engineering analysis and design, and pose significant computational challenges. Bringing solution and analysis to them motivated the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) method and also the variational multiscale version of the Arbitrary Lagrangian-Eulerian method (ALE-VMS). These two methods and their improved versions have been applied to a diverse set of challenging problems with a common core computational technology need. The classes of problems solved include free-surface and two-fluid flows, fluid-object and fluid-particle interaction, FSI, and flows with solid surfaces in fast, linear or rotational relative motion. Some of the most challenging FSI problems, including parachute FSI, wind-turbine FSI and arterial FSI, are being solved and analyzed with the DSD/SST and ALE-VMS methods as core technologies. Better accuracy and improved turbulence modeling were brought with the recently-introduced VMS version of the DSD/SST method, which is called DSD/SST-VMST (also ST-VMS). In specific classes of problems, such as parachute FSI, arterial FSI, ship hydrodynamics, fluid-object interaction, aerodynamics of flapping wings, and wind-turbine aerodynamics and FSI, the scope and accuracy of the modeling were increased with the special ALE-VMS and ST techniques targeting each of those classes of problems. This article provides an overview of how the core and special ALE-VMS and ST techniques are used in computational engineering analysis and design. The article includes an overview of three of the special ALE-VMS and ST techniques, which are just a few examples of the many special techniques that complement the core methods. The impact of the ALE-VMS and ST methods in engineering analysis and design are shown with examples of challenging problems solved and analyzed in parachute FSI, arterial FSI, ship hydrodynamics, aerodynamics of flapping wings, wind-turbine aerodynamics, and bridge-deck aerodynamics and vortex-induced vibrations.

    DOI

  • Computational wind-turbine analysis with the ALE-VMS and ST-VMS methods

    Yuri Bazilevs, Kenji Takizawa, Tayfun E. Tezduyar, Ming-Chen Hsu, Nikolay Kostov, Spenser McIntyre

    Computational Methods in Applied Sciences   33   355 - 386  2014年  [査読有り]

     概要を見る

    We provide an overview of the aerodynamic and FSI analysis of wind turbines the first three authors' teams carried out in recent years with the ALE-VMS and ST-VMS methods. The ALE-VMS method is the variational multiscale version of the Arbitrary Lagrangian-Eulerian (ALE) method. The VMS components are from the residual-based VMS (RBVMS) method. The ST-VMS method is the VMS version of the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) method. The techniques complementing these core methods include weak enforcement of the essential boundary conditions, NURBS-based isogeometric analysis, using NURBS basis functions in temporal representation of the rotor motion, mesh motion and also in remeshing, rotation representation with constant angular velocity, Kirchhoff-Love shell modeling of the rotor-blade structure, and full FSI coupling. The analysis cases include the aerodynamics of wind-turbine rotor and tower and the FSI that accounts for the deformation of the rotor blades. The specific wind turbines considered are NREL 5MW, NREL Phase VI and Micon 65/13M, all at full scale, and our analysis for NREL Phase VI and Micon 65/13M includes comparison with the experimental data.

    DOI

  • Fluid-structure interaction modeling of clusters of spacecraft parachutes with modified geometric porosity

    Takizawa, Kenji, Tezduyar, Tayfun E., Boben, Joseph, Kostov, Nikolay, Boswell, Cody, Buscher, Austin

    COMPUTATIONAL MECHANICS   52 ( 6 ) 1351 - 1364  2013年12月  [査読有り]

     概要を見る

    To increase aerodynamic performance, the geometric porosity of a ringsail spacecraft parachute canopy is sometimes increased, beyond the "rings" and "sails" with hundreds of "ring gaps" and "sail slits." This creates extra computational challenges for fluid-structure interaction (FSI) modeling of clusters of such parachutes, beyond those created by the lightness of the canopy structure, geometric complexities of hundreds of gaps and slits, and the contact between the parachutes of the cluster. In FSI computation of parachutes with such "modified geometric porosity," the flow through the "windows" created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the Homogenized Modeling of Geometric Porosity (HMGP), which was introduced to deal with the hundreds of gaps and slits. The flow needs to be actually resolved. All these computational challenges need to be addressed simultaneously in FSI modeling of clusters of spacecraft parachutes with modified geometric porosity. The core numerical technology is the Stabilized Space-Time FSI (SSTFSI) technique, and the contact between the parachutes is handled with the Surface-Edge-Node Contact Tracking (SENCT) technique. In the computations reported here, in addition to the SSTFSI and SENCT techniques and HMGP, we use the special techniques we have developed for removing the numerical spinning component of the parachute motion and for restoring the mesh integrity without a remesh. We present results for 2- and 3-parachute clusters with two different payload models.

    DOI

  • Finite element computation and experimental validation of sloshing in rectangular tanks

    Marcela A. Cruchaga, Ricardo S. Reinoso, Mario A. Storti, Diego J. Celentano, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   52 ( 6 ) 1301 - 1312  2013年12月  [査読有り]

     概要を見る

    Finite element computation and experimental validation of sloshing in rectangular tanks near the primary and secondary resonance modes are presented. In particular, 2D free-surface evolution is studied. The computational analysis is based on solving the Navier-Stokes equations of incompressible flows with a monolithic solver that includes a stabilized formulation and a Lagrangian tracking technique for updating the free surface. The time-dependent behavior of the numerical and experimental wave heights at different control points are compared, where the experimental data is collected using ultrasonic sensors and a shake table that controls the motion of the rectangular container.

    DOI

  • Computer modeling techniques for flapping-wing aerodynamics of a locust

    Takizawa, Kenji, Henicke, Bradley, Puntel, Anthony, Kostov, Nikolay, Tezduyar, Tayfun E.

    COMPUTERS & FLUIDS   85   125 - 134  2013年10月  [査読有り]

     概要を見る

    We present an overview of the special computer modeling techniques we have developed recently for flapping-wing aerodynamics of a locust. The wing motion and deformation data is from an actual locust, extracted from high-speed, multi-camera video recordings of the locust in a wind tunnel. The special techniques have been developed around our core computational technique, which is the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation. Here we use the version of the DSD/SST formulation derived in conjunction with the variational multiscale (VMS) method, and this version is called "DSD/SST-VMST." The special techniques are based on using, in the space-time flow computations, NURBS basis functions for the temporal representation of the motion and deformation of the locust wings. Temporal NURBS basis functions are used also in representation of the motion of the volume meshes computed and in remeshing. In this special-issue paper, we present a condensed version of the material from [1], concentrating on the flapping-motion modeling and computations, and also a temporal-order study from [2]. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI

  • Patient-specific computational analysis of the influence of a stent on the unsteady flow in cerebral aneurysms

    Takizawa, Kenji, Schjodt, Kathleen, Puntel, Anthony, Kostov, Nikolay, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   51 ( 6 ) 1061 - 1073  2013年06月  [査読有り]

     概要を見る

    We present a patient-specific computational analysis of the influence of a stent on the unsteady flow in cerebral aneurysms. The analysis is based on four different arterial models extracted form medical images, and the stent is placed across the neck of the aneurysm to reduce the flow circulation in the aneurysm. The core computational technique used in the analysis is the space-time (ST) version of the variational multiscale (VMS) method and is called "DSD/SST-VMST". The special techniques developed for this class of cardiovascular fluid mechanics computations are used in conjunction with the DSD/SST-VMST technique. The special techniques include NURBS representation of the surface over which the stent model and mesh are built, mesh generation with a reasonable resolution across the width of the stent wire and with refined layers of mesh near the arterial and stent surfaces, modeling the double-stent case, and quantitative assessment of the flow circulation in the aneurysm. We provide a brief overview of the special techniques, compute the unsteady flow patterns in the aneurysm for the four arterial models, and investigate in each case how those patterns are influenced by the presence of single and double stents.

    DOI

  • Patient-Specific Computational Fluid Mechanics of Cerebral Arteries with Aneurysm and Stent

    Kenji Takizawa, Kathleen Schjodt, Anthony Puntel, Nikolay Kostov, Tayfun E. Tezduyar

    Multiscale Simulations and Mechanics of Biological Materials     119 - 147  2013年03月  [査読有り]

     概要を見る

    We present patient-specific computational fluid mechanics analysis of blood flow in cerebral arteries with aneurysm and stent. The special arterial fluid mechanics techniques we have developed for this are used in conjunction with the core computational technique, which is the space-time version of the variational multiscale (VMS) method and is called "DST/SST-VMST." The special techniques include using a nonuniform rational basis spline for the spatial representation of the surface over which the stent mesh is built, mesh generation techniques for both the finite- and zero-thickness representations of the stent, techniques for generating refined layers of mesh near the arterial and stent surfaces, and models for representing double stents. We compute the unsteady flow patterns in the aneurysm and investigate how those patterns are influenced by the presence of single and double stents. We also compare the flow patterns obtained with the finite- and zero-thickness representations of the stent. This edition first published 2013 © 2013 John Wiley &amp
    Sons, Ltd.

    DOI

  • SPACE-TIME VMS METHODS FOR MODELING OF INCOMPRESSIBLE FLOWS AT HIGH REYNOLDS NUMBERS

    Takizawa, Kenji, Montes, Darren, McIntyre, Spenser, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   23 ( 2 ) 223 - 248  2013年02月  [査読有り]

     概要を見る

    Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation was developed for flow problems with moving interfaces and has been successfully applied to some of the most complex problems in that category. A new version of the DSD/SST method for incompressible flows, which has additional subgrid-scale representation features, is the space-time version of the residual-based variational multiscale (VMS) method. This new version, called DSD/SST-VMST and also Space-Time VMS (ST-VMS), provides a more comprehensive framework for the VMS method. We describe the ST-VMS method, including the embedded stabilization parameters, and assess its performance in computation of flow problems at high Reynolds numbers by comparing the results to experimental data. The computations, which include those with 3D airfoil geometries and spacecraft configurations, signal a promising future for the ST-VMS method.

    DOI

  • METHODS FOR FSI MODELING OF SPACECRAFT PARACHUTE DYNAMICS AND COVER SEPARATION

    Takizawa, Kenji, Montes, Darren, Fritze, Matthew, McIntyre, Spenser, Boben, Joseph, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   23 ( 2 ) 307 - 338  2013年02月  [査読有り]

     概要を見る

    Fluid-structure interaction (FSI) modeling of spacecraft parachutes involves a number of computational challenges beyond those encountered in a typical FSI problem. The stabilized space-time FSI (SSTFSI) technique serves as a robust and accurate core FSI method, and a number of special FSI methods address the computational challenges specific to spacecraft parachutes. Some spacecraft FSI problems involve even more specific computational challenges and require additional special methods. An example of that is the impulse ejection and parachute extraction of a protective cover used in a spacecraft. The computational challenges specific to this problem are related to the sudden changes in the parachute loads and sudden separation of the cover with very little initial clearance from the spacecraft. We describe the core and special FSI methods, and present the methods we use in FSI analysis of the parachute dynamics and cover separation, including the temporal NURBS representation in modeling the separation motion.

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  • CHALLENGES AND DIRECTIONS IN COMPUTATIONAL FLUID-STRUCTURE INTERACTION

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   23 ( 2 ) 215 - 221  2013年02月  [査読有り]

     概要を見る

    In this lead paper of the special issue, we provide some comments on challenges and directions in computational fluid-structure interaction (FSI). We briefly discuss the significance of computational FSI methods, their components, moving-mesh and nonmoving-mesh methods, mesh moving and remeshing concepts, and FSI coupling techniques.

    DOI

  • SUPG and discontinuity-capturing methods for coupled fluid mechanics and electrochemical transport problems

    Kler Pablo A, Dalcin Lisandro D, Paz Rodrigo R, Tezduyar Tayfun E

    Computational Mechanics   51 ( 2 ) 171 - 185  2013年  [査読有り]

    DOI

  • Computational Fluid-Structure Interaction: Methods and Applications

    Yuri Bazilevs, Kenji Takizawa, Tayfun E. Tezduyar

    Computational Fluid-Structure Interaction: Methods and Applications    2012年12月  [査読有り]

     概要を見る

    Computational Fluid-Structure Interaction: Methods and Applications takes the reader from the fundamentals of computational fluid and solid mechanics to the state-of-the-art in computational FSI methods, special FSI techniques, and solution of real-world problems. Leading experts in the field present the material using a unique approach that combines advanced methods, special techniques, and challenging applications. This book begins with the differential equations governing the fluid and solid mechanics, coupling conditions at the fluid-solid interface, and the basics of the finite element method. It continues with the ALE and space-time FSI methods, spatial discretization and time integration strategies for the coupled FSI equations, solution techniques for the fully-discretized coupled equations, and advanced FSI and space-time methods. It ends with special FSI techniques targeting cardiovascular FSI, parachute FSI, and wind-turbine aerodynamics and FSI. Key features: First book to address the state-of-the-art in computational FSI Combines the fundamentals of computational fluid and solid mechanics, the state-of-the-art in FSI methods, and special FSI techniques targeting challenging classes of real-world problems Covers modern computational mechanics techniques, including stabilized, variational multiscale, and space-time methods, isogeometric analysis, and advanced FSI coupling methods. Is in full color, with diagrams illustrating the fundamental concepts and advanced methods and with insightful visualization illustrating the complexities of the problems that can be solved with the FSI methods covered in the book. Authors are award winning, leading global experts in computational FSI, who are known for solving some of the most challenging FSI problems. Computational Fluid-Structure Interaction: Methods and Applications is a comprehensive reference for researchers and practicing engineers who would like to advance their existing knowledge on these subjects. It is also an ideal text for graduate and senior-level undergraduate courses in computational fluid mechanics and computational FSI. © 2013 John Wiley &amp
    Sons, Ltd.

    DOI

  • bringing them down safely

    Takizawa, Kenji, Tezduyar, Tayfun E.

    MECHANICAL ENGINEERING   134 ( 12 ) 34 - 37  2012年12月  [査読有り]

    DOI

  • Space-time techniques for computational aerodynamics modeling of flapping wings of an actual locust

    Takizawa, Kenji, Henicke, Bradley, Puntel, Anthony, Kostov, Nikolay, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   50 ( 6 ) 743 - 760  2012年12月  [査読有り]

     概要を見る

    We present the special space-time computational techniques we have introduced recently for computational aerodynamics modeling of flapping wings of an actual locust. These techniques have been designed to be used with the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, which is the core computational technique. The DSD/SST formulation was developed for flow problems with moving interfaces and was elevated to newer versions over the years, including the space-time version of the residual-based variational multiscale (VMS) method, which is called "DSD/SST-VMST" and used in the computations reported here. The special space-time techniques are based on using, in the space-time flow computations, NURBS basis functions for the temporal representation of the motion and deformation of the locust wings. The motion and deformation data is extracted from the high-speed, multi-camera video recordings of a locust in a wind tunnel. In addition, temporal NURBS basis functions are used in representation of the motion and deformation of the volume meshes computed and also in remeshing. These ingredients provide an accurate and efficient way of dealing with the wind tunnel data and the mesh. The computations demonstrate the effectiveness of the core and special space-time techniques in modeling the aerodynamics of flapping wings, with the wing motion and deformation coming from an actual locust.

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  • Space-time computational analysis of bio-inspired flapping-wing aerodynamics of a micro aerial vehicle

    Takizawa, Kenji, Kostov, Nikolay, Puntel, Anthony, Henicke, Bradley, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   50 ( 6 ) 761 - 778  2012年12月  [査読有り]

     概要を見る

    We present a detailed computational analysis of bio-inspired flapping-wing aerodynamics of a micro aerial vehicle (MAV). The computational techniques used include the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, which serves as the core computational technique. The DSD/SST formulation is a moving-mesh technique, and in the computations reported here we use the space-time version of the residual-based variational multiscale (VMS) method, which is called "DSD/SST-VMST." The motion and deformation of the wings are based on data extracted from the high-speed, multi-camera video recordings of a locust in a wind tunnel. A set of special space-time techniques are also used in the computations in conjunction with the DSD/SST method. The special techniques are based on using, in the space-time flow computations, NURBS basis functions for the temporal representation of the motion and deformation of the wings and for the mesh moving and remeshing. The computational analysis starts with the computation of the base case, and includes computations with increased temporal and spatial resolutions compared to the base case. In increasing the temporal resolution, we separately test increasing the temporal order, the number of temporal subdivisions, and the frequency of remeshing. In terms of the spatial resolution, we separately test increasing the wing-mesh refinement in the normal and tangential directions and changing the way node connectivities are handled at the wingtips. The computational analysis also includes using different combinations of wing configurations for the MAV and investigating the beneficial and disruptive interactions between the wings and the role of wing camber and twist.

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  • Patient-specific computer modeling of blood flow in cerebral arteries with aneurysm and stent

    Takizawa, Kenji, Schjodt, Kathleen, Puntel, Anthony, Kostov, Nikolay, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   50 ( 6 ) 675 - 686  2012年12月  [査読有り]

     概要を見る

    We present the special arterial fluid mechanics techniques we have developed for patient-specific computer modeling of blood flow in cerebral arteries with aneurysm and stent. These techniques are used in conjunction with the core computational technique, which is the space-time version of the variational multiscale (VMS) method and is called "DST/SST-VMST." The special techniques include using NURBS for the spatial representation of the surface over which the stent mesh is built, mesh generation techniques for both the finite-and zero-thickness representations of the stent, techniques for generating refined layers of mesh near the arterial and stent surfaces, and models for representing double stent. We compute the unsteady flow patterns in the aneurysm and investigate how those patterns are influenced by the presence of single and double stents. We also compare the flow patterns obtained with the finite- and zero-thickness representations of the stent.

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  • Fluid-structure interaction modeling of ringsail parachutes with disreefing and modified geometric porosity

    Takizawa, Kenji, Fritze, Matthew, Montes, Darren, Spielman, Timothy, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   50 ( 6 ) 835 - 854  2012年12月  [査読有り]

     概要を見る

    Fluid-structure interaction (FSI) modeling of parachutes poses a number of computational challenges. These include the lightness of the parachute canopy compared to the air masses involved in the parachute dynamics, in the case of ringsail parachutes the geometric porosity created by the construction of the canopy from "rings" and "sails" with hundreds of "ring gaps" and "sail slits," in the case of parachute clusters the contact between the parachutes, and "disreefing" from one stage to another when the parachute is used in multiple stages. The Team for Advanced Flow Simulation and Modeling (T*AFSM) has been successfully addressing these computational challenges with the Stabilized Space-Time FSI (SSTFSI) technique, which was developed and improved over the years by the T*AFSM and serves as the core numerical technology, and a number of special techniques developed in conjunction with the SSTFSI technique. The quasi-direct and direct coupling techniques developed by the T*AFSM, which are applicable to cases with nonmatching fluid and structure meshes at the interface, yield more robust algorithms for FSI computations where the structure is light. The special technique used in dealing with the geometric complexities of the rings and sails is the homogenized modeling of geometric porosity (HMGP), which was developed and improved in recent years by the T*AFSM. The surface-edge-node contact tracking (SENCT) technique was introduced by the T*AFSM as a contact algorithm where the objective is to prevent the structural surfaces from coming closer than a minimum distance in an FSI computation. The recently-introduced conservative version of the SENCT technique is more robust and is now an essential technology in the parachute cluster computations carried out by the T*AFSM. As an additional computational challenge, the parachute canopy might, by design, have some of its panels and sails removed. In FSI computation of parachutes with such "modified geometric porosity," the flowthrough the "windows" created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the HMGP and needs to be actually resolved during the FSI computation. In this paper we focus on parachute disreefing, including the disreefing of parachute clusters, and parachutes with modified geometric porosity, including the reefed stages of such parachutes. We describe the additional special techniques we have developed to address the challenges involved and report FSI computations for parachutes and parachute clusters with disreefing and modified geometric porosity.

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  • Computational fluid mechanics and fluid-structure interaction PREFACE

    Takizawa, Kenji, Bazilevs, Yuri, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   50 ( 6 ) 665 - 665  2012年12月  [査読有り]

    DOI

  • Computational analysis of noise reduction devices in axial fans with stabilized finite element formulations

    A. Corsini, F. Rispoli, A. G. Sheard, T. E. Tezduyar

    COMPUTATIONAL MECHANICS   50 ( 6 ) 695 - 705  2012年12月  [査読有り]

     概要を見る

    The paper illustrates how a computational fluid mechanic technique, based on stabilized finite element formulations, can be used in analysis of noise reduction devices in axial fans. Among the noise control alternatives, the study focuses on the use of end-plates fitted at the blade tips to control the leakage flow and the related aeroacoustic sources. The end-plate shape is configured to govern the momentum transfer to the swirling flow at the blade tip. This flow control mechanism has been found to have a positive link to the fan aeroacoustics. The complex physics of the swirling flow at the tip, developing under the influence of the end-plate, is governed by the rolling up of the jet-like leakage flow. The RANS modelling used in the computations is based on the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin methods, supplemented with the DRDJ stabilization. Judicious determination of the stabilization parameters involved is also a part of our computational technique and is described for each component of the stabilized formulation. We describe the flow physics underlying the design of the noise control device and illustrate the aerodynamic performance. Then we investigate the numerical performance of the formulation by analysing the inner workings of the stabilization operators and of their interaction with the turbulence model.

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  • SPACE-TIME FLUID-STRUCTURE INTERACTION METHODS

    Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   22 ( SUPPL.2 )  2012年08月  [査読有り]

     概要を見る

    Since its introduction in 1991 for computation of flow problems with moving boundaries and interfaces, the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation has been applied to a diverse set of challenging problems. The classes of problems computed include free-surface and two-fluid flows, fluid-object, fluid-particle and fluid-structure interaction (FSI), and flows with mechanical components in fast, linear or rotational relative motion. The DSD/SST formulation, as a core technology, is being used for some of the most challenging FSI problems, including parachute modeling and arterial FSI. Versions of the DSD/SST formulation introduced in recent years serve as lower-cost alternatives. More recent variational multiscale (VMS) version, which is called DSD/SST-VMST (and also ST-VMS), has brought better computational accuracy and serves as a reliable turbulence model. Special space-time FSI techniques introduced for specific classes of problems, such as parachute modeling and arterial FSI, have increased the scope and accuracy of the FSI modeling in those classes of computations. This paper provides an overview of the core space-time FSI technique, its recent versions, and the special space-time FSI techniques. The paper includes test computations with the DSD/SST-VMST technique.

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  • ALE-VMS AND ST-VMS METHODS FOR COMPUTER MODELING OF WIND-TURBINE ROTOR AERODYNAMICS AND FLUID-STRUCTURE INTERACTION

    Bazilevs, Yuri, Hsu, Ming-Chen, Takizawa, Kenji, Tezduyar, Tayfun E.

    MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES   22 ( SUPPL.2 )  2012年08月  [査読有り]

     概要を見る

    We provide an overview of the Arbitrary Lagrangian-Eulerian Variational Multiscale (ALE-VMS) and Space-Time Variational Multiscale (ST-VMS) methods we have developed for computer modeling of wind-turbine rotor aerodynamics and fluid-structure interaction (FSI). The related techniques described include weak enforcement of the essential boundary conditions, Kirchhoff-Love shell modeling of the rotor-blade structure, NURBS-based isogeometric analysis, and full FSI coupling. We present results from application of these methods to computer modeling of NREL 5MW and NREL Phase VI wind-turbine rotors at full scale, including comparison with experimental data.

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  • Space-Time and ALE-VMS Techniques for Patient-Specific Cardiovascular Fluid-Structure Interaction Modeling

    Takizawa, Kenji, Bazilevs, Yuri, Tezduyar, Tayfun E.

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   19 ( 2 ) 171 - 225  2012年06月  [査読有り]

     概要を見る

    This is an extensive overview of the core and special space-time and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the authors' research teams for patient-specific cardiovascular fluid-structure interaction (FSI) modeling. The core techniques are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized Space-Time formulation, and the stabilized space-time FSI technique. The special techniques include methods for calculating an estimated zero-pressure arterial geometry, prestressing of the blood vessel wall, a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, techniques for using variable arterial wall thickness, mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, a recipe for pre-FSI computations that improve the convergence of the FSI computations, the Sequentially-Coupled Arterial FSI technique and its multiscale versions, techniques for the projection of fluid-structure interface stresses, calculation of the wall shear stress and oscillatory shear index, arterial-surface extraction and boundary condition techniques, and a scaling technique for specifying a more realistic volumetric flow rate. With results from earlier computations, we show how these core and special FSI techniques work in patient-specific cardiovascular simulations.

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  • Computational Methods for Parachute Fluid-Structure Interactions

    Takizawa, Kenji, Tezduyar, Tayfun E.

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   19 ( 1 ) 125 - 169  2012年03月  [査読有り]

     概要を見る

    The computational challenges posed by fluid-structure interaction (FSI) modeling of parachutes include the lightness of the parachute canopy compared to the air masses involved in the parachute dynamics, in the case of "ringsail" parachutes the geometric complexities created by the construction of the canopy from "rings" and "sails" with hundreds of ring "gaps" and sail "slits", and in the case of parachute clusters the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T*AFSM) has successfully addressed these computational challenges with the Stabilized Space-Time FSI (SSTFSI) technique, which was developed and improved over the years by the T*AFSM and serves as the core numerical technology, and a number of special techniques developed in conjunction with the SSTFSI technique. The quasi-direct and direct coupling techniques developed by the T * AFSM, which are applicable to cases with incompatible fluid and structure meshes at the interface, yield more robust algorithms for FSI computations where the structure is light and therefore more sensitive to the variations in the fluid dynamics forces. The special technique used in dealing with the geometric complexities of the rings and sails is the Homogenized Modeling of Geometric Porosity, which was developed and improved in recent years by the T*AFSM. The Surface-Edge-Node Contact Tracking (SENCT) technique was introduced by the T*AFSM as a contact algorithm where the objective is to prevent the structural surfaces from coming closer than a minimum distance in an FSI computation. The recently-introduced conservative version of the SENCT technique is more robust and is now an essential technology in the parachute cluster computations carried out by the T*AFSM. We provide an overview of the core and special techniques developed by the T*AFSM, present single-parachute FSI computations carried out for design-parameter studies, and report FSI computation and dynamical analysis of two-parachute clusters.

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  • Special Issue on Computational Fluid Mechanics and Fluid-Structure Interaction Preface

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   79 ( 1 )  2012年01月  [査読有り]

    DOI

  • Space-Time Computational Techniques for the Aerodynamics of Flapping Wings

    Takizawa, Kenji, Henicke, Bradley, Puntel, Anthony, Spielman, Timothy, Tezduyar, Tayfun E.

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   79 ( 1 )  2012年01月  [査読有り]

     概要を見る

    We present the special space-time computational techniques we have introduced recently for computation of flow problems with moving and deforming solid surfaces. The techniques have been designed in the context of the deforming-spatial-domain/stabilized space-time formulation, which was developed by the Team for Advanced Flow Simulation and Modeling for computation of flow problems with moving boundaries and interfaces. The special space-time techniques are based on using, in the space-time flow computations, non-uniform rational B-splines (NURBS) basis functions for the temporal representation of the motion and deformation of the solid surfaces and also for the motion and deformation of the volume meshes computed. This provides a better temporal representation of the solid surfaces and a more effective way of handling the volume-mesh motion. We apply these techniques to computation of the aerodynamics of flapping wings, specifically locust wings, where the prescribed motion and deformation of the wings are based on digital data extracted from the videos of the locust in a wind tunnel. We report results from the preliminary computations. [DOI: 10.1115/1.4005073]

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  • Fluid-Structure Interaction Modeling of Spacecraft Parachutes for Simulation-Based Design

    Takizawa, Kenji, Spielman, Timothy, Moorman, Creighton, Tezduyar, Tayfun E.

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   79 ( 1 )  2012年01月  [査読有り]

     概要を見る

    Even though computer modeling of spacecraft parachutes involves a number of numerical challenges, advanced techniques developed in recent years for fluid-structure interaction (FSI) modeling in general and for parachute FSI modeling specifically have made simulation-based design studies possible. In this paper we focus on such studies for a single main parachute to be used with the Orion spacecraft. Although these large parachutes are typically used in clusters of two or three parachutes, studies for a single parachute can still provide valuable information for performance analysis and design and can be rather extensive. The major challenges in computer modeling of a single spacecraft parachute are the FSI between the air and the parachute canopy and the geometric complexities created by the construction of the parachute from "rings" and "sails" with hundreds of gaps and slits. The Team for Advanced Flow Simulation and Modeling has successfully addressed the computational challenges related to the FSI and geometric complexities, and has also been devising special procedures as needed for specific design parameter studies. In this paper we present parametric studies based on the suspension line length, canopy loading, and the length of the overinflation control line. [DOI: 10.1115/1.4005070]

    DOI

  • Computer Modeling of Wave-Energy Air Turbines With the SUPG/PSPG Formulation and Discontinuity-Capturing Technique

    A. Corsini, F. Rispoli, T. E. Tezduyar

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   79 ( 1 )  2012年01月  [査読有り]

     概要を見る

    We present a computational fluid mechanics technique for modeling of wave-energy air turbines, specifically the Wells turbine. In this type of energy conversion, the wave motion is converted to an oscillating airflow in a duct with the turbine. This is a self-rectifying turbine in the sense that it maintains the same direction of rotation as the airflow changes direction. The blades of the turbine are symmetrical, and here we consider straight and swept blades, both with constant chord. The turbulent flow physics involved in the complex, unsteady flow is governed by nonequilibrium behavior, and we use a stabilized formulation to address the related challenges in the context of RANS modeling. The formulation is based on the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin methods, supplemented with the DRDJ stabilization. Judicious determination of the stabilization parameters involved is also a part of our computational technique and is described for each component of the stabilized formulation. We compare the numerical performance of the formulation with and without the DRDJ stabilization and present the computational results obtained for the two blade configurations with realistic airflow data. [DOI: 10.1115/1.4005060]

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  • A Comparative Study Based on Patient-Specific Fluid-Structure Interaction Modeling of Cerebral Aneurysms

    Takizawa, Kenji, Brummer, Tyler, Tezduyar, Tayfun E., Chen, Peng R.

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   79 ( 1 )  2012年01月  [査読有り]

     概要を見る

    We present an extensive comparative study based on patient-specific fluid-structure interaction (FSI) modeling of cerebral aneurysms. We consider a total of ten cases, at three different locations, half of which ruptured. We use the stabilized space-time FSI technique developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM), together with a number of special techniques targeting arterial FSI modeling, which were also developed by the T*AFSM. What we look at in our comparisons includes the wall shear stress, oscillatory shear index and the arterial-wall stress and stretch. We also investigate how simpler approaches to computer modeling of cerebral aneurysms perform compared to FSI modeling. [DOI: 10.1115/1.4005071]

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  • Numerical-performance studies for the stabilized space-time computation of wind-turbine rotor aerodynamics

    Takizawa, Kenji, Henicke, Bradley, Montes, Darren, Tezduyar, Tayfun E., Hsu, Ming-Chen, Bazilevs, Yuri

    COMPUTATIONAL MECHANICS   48 ( 6 ) 647 - 657  2011年12月  [査読有り]

     概要を見る

    We present our numerical-performance studies for 3D wind-turbine rotor aerodynamics computation with the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation. The computation is challenging because of the large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. As the test case, we use the NREL 5MW offshore baseline wind-turbine rotor. We compute the problem with both the original version of the DSD/SST formulation and the version with an advanced turbulence model. The DSD/SST formulation with the turbulence model is a recently-introduced space-time version of the residual-based variational multiscale method. We include in our comparison as reference solution the results obtained with the residual-based variational multiscale Arbitrary Lagrangian-Eulerian method using NURBS for spatial discretization. We test different levels of mesh refinement and different definitions for the stabilization parameter embedded in the "least squares on incompressibility constraint" stabilization. We compare the torque values obtained.

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  • Space-time fluid-structure interaction modeling of patient-specific cerebral aneurysms

    Tezduyar, Tayfun E., Takizawa, Kenji, Brummer, Tyler, Chen, Peng R.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING   27 ( 11 ) 1665 - 1710  2011年11月  [査読有り]

     概要を見る

    We provide an extensive overview of the core and special techniques developed earlier by the Team for Advanced Flow Simulation and Modeling (T star AFSM) for space-time fluid-structure interaction (FSI) modeling of patient-specific cerebral aneurysms. The core FSI techniques are the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation and the stabilized space-time FSI (SSTFSI) technique. The special techniques include techniques for calculating an estimated zero-pressure (EZP) arterial geometry, a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, techniques for using variable arterial wall thickness, mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, a recipe for pre-FSI computations that improve the convergence of the FSI computations, the Sequentially-Coupled Arterial FSI (SCAFSI) technique and its multiscale versions, techniques for the projection of fluid-structure interface stresses, calculation of the wall shear stress (WSS) and calculation of the oscillatory shear index (OSI) and arterial-surface extraction and boundary condition techniques. We show how these techniques work with results from earlier computations. We also describe the arterial FSI techniques developed and implemented recently by the T star AFSM and present a sample from a wide set of patient-specific cerebral-aneurysm models we computed recently. Copyright (C) 2011 John Wiley & Sons, Ltd.

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  • Stabilized space-time computation of wind-turbine rotor aerodynamics

    Takizawa, Kenji, Henicke, Bradley, Tezduyar, Tayfun E., Hsu, Ming-Chen, Bazilevs, Yuri

    COMPUTATIONAL MECHANICS   48 ( 3 ) 333 - 344  2011年09月  [査読有り]

     概要を見る

    We show how we use the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation for accurate 3D computation of the aerodynamics of a wind-turbine rotor. As the test case, we use the NREL 5MW offshore baseline wind-turbine rotor. This class of computational problems are rather challenging, because they involve large Reynolds numbers and rotating turbulent flows, and computing the correct torque requires an accurate and meticulous numerical approach. We compute the problem with both the original version of the DSD/SST formulation and a recently introduced version with an advanced turbulence model. The DSD/SST formulation with the advanced turbulence model is a space-time version of the residual-based variational multiscale method. We compare our results to those reported recently, which were obtained with the residual-based variational multiscale Arbitrary Lagrangian-Eulerian method using NURBS for spatial discretization and which we take as the reference solution. While the original DSD/SST formulation yields torque values not far from the reference solution, the DSD/SST formulation with the variational multiscale turbulence model yields torque values very close to the reference solution.

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  • Special issue on computational fluid mechanics and fluid-structure interaction Preface

    Bazilevs, Yuri, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   48 ( 3 ) 245 - 245  2011年09月  [査読有り]

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  • Space-time SUPG finite element computation of shallow-water flows with moving shorelines

    Shinsuke Takase, Kazuo Kashiyama, Seizo Tanaka, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   48 ( 3 ) 293 - 306  2011年09月  [査読有り]

     概要を見る

    We show that combination of the Deforming-Spatial-Domain/Stabilized Space-Time and the Streamline-Upwind/Petrov-Galerkin formulations can be used quite effectively for computation of shallow-water flows with moving shorelines. The combined formulation is supplemented with a stabilization parameter that was originally introduced for compressible flows, a compressible-flow shock-capturing parameter adapted for shallow-water flows, and remeshing based on using a background mesh. We present a number of test computations and provide comparisons to theoretical results, experimental data and results computed with nonmoving meshes.

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  • Space-time FSI modeling and dynamical analysis of spacecraft parachutes and parachute clusters

    Takizawa, Kenji, Spielman, Timothy, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   48 ( 3 ) 345 - 364  2011年09月  [査読有り]

     概要を見る

    Computer modeling of spacecraft parachutes, which are quite often used in clusters of two or three large parachutes, involves fluid-structure interaction (FSI) between the parachute canopy and the air, geometric complexities created by the construction of the parachute from "rings" and "sails" with hundreds of gaps and slits, and the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T*AFSM) has successfully addressed the computational challenges related to the FSI and geometric complexities, and recently started addressing the challenges related to the contact between the parachutes of a cluster. The core numerical technology is the stabilized space-time FSI technique developed and improved over the years by the T*AFSM . The special technique used in dealing with the geometric complexities is the Homogenized Modeling of Geometric Porosity, which was also developed and improved in recent years by the T*AFSM . In this paper we describe the technique developed by the T*AFSM for modeling, in the context of an FSI problem, the contact between two structural surfaces. We show how we use this technique in dealing with the contact between parachutes. We present the results obtained with the FSI computation of parachute clusters, the related dynamical analysis, and a special decomposition technique for parachute descent speed to make that analysis more informative. We also present a special technique for extracting from a parachute FSI computation model parameters, such as added mass, that can be used in fast, approximate engineering analysis models for parachute dynamics.

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  • Multiscale space-time fluid-structure interaction techniques

    Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   48 ( 3 ) 247 - 267  2011年09月  [査読有り]

     概要を見る

    We present the multiscale space-time techniques we have developed for fluid-structure interaction (FSI) computations. Some of these techniques are multiscale in the way the time integration is performed (i.e. temporally multiscale), some are multiscale in the way the spatial discretization is done (i.e. spatially multiscale), and some are in the context of the sequentially-coupled FSI (SCFSI) techniques developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM). In the multiscale SCFSI technique, the FSI computational effort is reduced at the stage we do not need it and the accuracy of the fluid mechanics (or structural mechanics) computation is increased at the stage we need accurate, detailed flow (or structure) computation. As ways of increasing the computational accuracy when or where needed, and beyond just increasing the mesh refinement or decreasing the time-step size, we propose switching to more accurate versions of the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, using more polynomial power for the basis functions of the spatial discretization or time integration, and using an advanced turbulence model. Specifically, for more polynomial power in time integration, we propose to use NURBS, and as an advanced turbulence model to be used with the DSD/SST formulation, we introduce a space-time version of the residual-based variational multiscale method. We present a number of test computations showing the performance of the multiscale space-time techniques we are proposing. We also present a stability and accuracy analysis for the higher-accuracy versions of the DSD/SST formulation.

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  • A parallel sparse algorithm targeting arterial fluid mechanics computations

    Manguoglu, Murat, Takizawa, Kenji, Sameh, Ahmed H., Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   48 ( 3 ) 377 - 384  2011年09月  [査読有り]

     概要を見る

    Iterative solution of large sparse nonsymmetric linear equation systems is one of the numerical challenges in arterial fluid-structure interaction computations. This is because the fluid mechanics parts of the fluid + structure block of the equation system that needs to be solved at every nonlinear iteration of each time step corresponds to incompressible flow, the computational domains include slender parts, and accurate wall shear stress calculations require boundary layer mesh refinement near the arterial walls. We propose a hybrid parallel sparse algorithm, domain-decomposing parallel solver (DDPS), to address this challenge. As the test case, we use a fluid mechanics equation system generated by starting with an arterial shape and flow field coming from an FSI computation and performing two time steps of fluid mechanics computation with a prescribed arterial shape change, also coming from the FSI computation. We show how the DDPS algorithm performs in solving the equation system and demonstrate the scalability of the algorithm.

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  • Comments on paratrooper-separation modeling with the DSD/SST formulation and FOIST

    Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   66 ( 8 ) 1068 - 1072  2011年07月  [査読有り]

     概要を見る

    We provide a brief chronological background on the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, its use in aerodynamic modeling of a paratrooper separating from an aircraft, and the fluid-object interactions subcomputation technique (FOIST). Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Comments on 'Adiabatic shock capturing in perfect gas hypersonic flows'

    Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   66 ( 7 ) 935 - 938  2011年07月  [査読有り]

     概要を見る

    Some comments are provided on the shock-capturing techniques and stabilization parameters used in a recent paper (B. S. Kirk, Int. J. Numer. Meth. Fluids 2009; DOI: 10.1002/fld.2195) in conjunction with the SUPG formulation of compressible flows. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Comment on "Three-Dimensional Aerodynamic Simulations of Jumping Paratroopers and Falling Cargo Payloads"

    Tayfun E. Tezduyar

    JOURNAL OF AIRCRAFT   48 ( 4 ) 1471 - 1472  2011年07月  [査読有り]

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  • Stabilized finite element computation of NOx emission in aero-engine combustors

    A. Corsini, F. Rispoli, T. E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 254 - 270  2011年01月  [査読有り]

     概要を見る

    A stabilized finite element formulation for the computation of turbulent reacting flows and NOx emission is presented. The method is based on the Streamline-Upwind/Petrov-Galerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) formulations, complemented with directionally formulated diffusion for reaction-dominated flows ('DRDJ' stabilization). The stabilized formulation is applied to the advection-diffusion-reaction equations governing the turbulent combustion and the NOx emission equations based on the thermal and the N2O pathways. The simulation is carried out for a co-axial burner, with a non-premixed swirling flame. The burner is operated at high pressure to represent the take-off conditions for an aero-engine. The vortical patterns of the swirling flame are analyzed together with the temperature field and flame position. The NOx formation processes are discussed, providing insight into the features of thermal and N2O mechanisms. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • SPACE-TIME FSI MODELING OF RINGSAIL PARACHUTE CLUSTERS

    Takizawa, Kenji, Spielman, Timothy, Tezduyar, Tayfun E.

    TEXTILE COMPOSITES AND INFLATABLE STRUCTURES V (STRUCTURAL MEMBRANES 2011)     55 - 66  2011年  [査読有り]

     概要を見る

    The computational challenges posed by fluid-structure interaction (FSI) modeling of ringsail parachute clusters include the lightness of the membrane and cable structure of the canopy compared to the air masses involved in the parachute dynamics, geometric complexities created by the construction of the canopy from "rings" and "sails" with hundreds of ring gaps and sail slits, and the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T star AFSM) has successfully addressed these computational challenges with the Stabilized Space-Time FSI technique (SSTFSI), which was developed and improved over the years by the T star AFSM and serves as the core numerical technology, and a number of special techniques developed in conjunction with the SSTFSI. We present the results obtained with the FSI computation of parachute clusters and the related dynamical analysis.

  • SPACE-TIME FSI MODELING AND DYNAMICAL ANALYSIS OF RINGSAIL PARACHUTE CLUSTERS

    Takizawa, Kenji, Spielman, Timothy, Tezduyar, Tayfun E.

    COMPUTATIONAL METHODS FOR COUPLED PROBLEMS IN SCIENCE AND ENGINEERING IV     43 - 54  2011年  [査読有り]

     概要を見る

    Computer modeling of ringsail parachute clusters involves fluid structure interaction (FSI) between the parachute canopy and the air, geometric complexities created by the construction of the parachute from "rings" and "sails" with hundreds of gaps and slits, and the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T star AFSM) has successfully addressed the computational challenges related to the FSI and geometric complexities, and recently started addressing the challenges related to the contact between the parachutes of a cluster. This is being accomplished with the Stabilized Space-Time FSI technique, which was developed and improved over the years by the T star AFSM and serves as the core numerical technology, and the special techniques developed by the T star AFSM to deal with the geometric complexities and the contact between parachutes. We present the results obtained with the FSI computation of parachute clusters and the related dynamical analysis.

  • Patient-specific arterial fluid-structure interaction modeling of cerebral aneurysms

    Takizawa, Kenji, Moorman, Creighton, Wright, Samuel, Purdue, John, McPhail, Travis, Chen, Peng R., Warren, Joe, Tezduyar, Tayfun E.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 308 - 323  2011年01月  [査読有り]

     概要を見る

    We address the computational challenges related to the extraction of the arterial-lumen geometry, mesh generation and starting-point determination in the computation of arterial fluid-structure interactions (FSI) with patient-specific data. The methods we propose here to address those challenges include techniques for constructing suitable cutting planes at the artery inlets and outlets and specifying on those planes proper boundary conditions for the fluid mechanics, structural mechanics and fluid mesh motion and a technique for the improved calculation of an estimated zero-pressure arterial geometry. We use the stabilized space-time FSI technique, together with a number of special techniques recently developed for arterial FSI. We focus on three patient-specific cerebral artery segments with aneurysm, where the lumen geometries are extracted from 3D rotational angiography. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Nested and parallel sparse algorithms for arterial fluid mechanics computations with boundary layer mesh refinement

    Manguoglu, Murat, Takizawa, Kenji, Sameh, Ahmed H., Tezduyar, Tayfun E.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 135 - 149  2011年01月  [査読有り]

     概要を見る

    Arterial fluid-structure interaction (FSI) computations involve a number of numerical challenges. Because blood flow is incompressible, iterative solution of the fluid mechanics part of the linear equation system at every nonlinear iteration of each time step is one of those challenges, especially for computations over slender domains and in the presence of boundary layer mesh refinement. In this paper we address that challenge. As test cases, we use equation systems from stabilized finite element computation of a bifurcating middle cerebral artery segment with aneurysm, with thin layers of elements near the arterial wall. We show how the preconditioning techniques, we propose for solving these large sparse nonsymmetric systems, perform at different time steps of the computation over a cardiac cycle. We also present a new hybrid parallel sparse linear system solver 'DD-Spike' and demonstrate its scalability. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • MULTISCALE SPACE-TIME COMPUTATION TECHNIQUES

    Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL METHODS FOR COUPLED PROBLEMS IN SCIENCE AND ENGINEERING IV     611 - 622  2011年  [査読有り]

     概要を見る

    A number of multiscale space time techniques have been developed recently by the Team for Advanced Flow Simulation and Modeling (T star AFSM) for fluid structure interaction computations. As part of that, we have introduced a space time version of the residual-based variational multiscale method. It has been designed in the context of the Deforming-Spatial-Domain/Stabilized Space Time formulation, which was developed earlier by the T star AFSM for computation of flow problems with moving boundaries and interfaces. We describe this multiscale space time technique, and present results from test computations.

  • MULTISCALE SEQUENTIALLY-COUPLED FSI COMPUTATION IN PARACHUTE MODELING

    Takizawa, Kenji, Wright, Samuel, Christopher, Jason, Tezduyar, Tayfun E.

    TEXTILE COMPOSITES AND INFLATABLE STRUCTURES V (STRUCTURAL MEMBRANES 2011)     385 - 396  2011年  [査読有り]

     概要を見る

    We describe how the spatially multiscale Sequentially-Coupled Fluid-Structure Interaction (SCFSI) techniques we have developed, specifically the "SCFSI M2C", which is spatially multiscale for the structural mechanics part, can be used for increasing the accuracy of the membrane and cable structural mechanics solution in parachute FSI computations. The SCFSI M2C technique is used here in conjunction with the Stabilized Space-Time FSI (SSTFSI) technique, which was developed and improved over the years by the Team for Advanced Flow Simulation and Modeling (T star AFSM) and serves as the core numerical technology, and a number of special parachute FSI techniques developed by the T star AFSM in conjunction with the SSTFSI technique.

  • Influencing factors in image-based fluid-structure interaction computation of cerebral aneurysms

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 324 - 340  2011年01月  [査読有り]

     概要を見る

    We review and summarize our research activities in fluid-structure interaction (FSI) analysis of cerebral aneurysms using anatomically realistic geometry models based on medical images. Emphasis is placed on influencing factors in computational FSI, and their role and clinical implications are discussed in terms of the wall shear stress (WSS). The key factors are: (1) arterial and aneurysm geometries, (2) wall structure modeling, (3) blood pressure, (4) outflow conditions and (5) inflow conditions. Among these, we find the impact of the arterial and aneurysm geometries to be the most significant. Blood pressure also has a significant impact on the WSS distribution; a hypothetical hypertensive blood pressure condition could help estimate the rupture risk for an aneurysm. We find the other three factors to be minor compared with the arterial and aneurysm geometries and blood pressure, although the level of influence could be unique to the middle cerebral artery aneurysms that we have been focusing on in our studies. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Fluid-structure interaction modeling of ringsail parachute clusters

    Takizawa K, Spielman T, Tezduyar T.E

    AIP Conference Proceedings   1376   7 - 11  2011年  [査読有り]

    DOI

  • Fluid-structure interaction modeling of parachute clusters

    Takizawa, Kenji, Wright, Samuel, Moorman, Creighton, Tezduyar, Tayfun E.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 286 - 307  2011年01月  [査読有り]

     概要を見る

    We address some of the computational challenges involved in fluid-structure interaction (FSI) modeling of clusters of ringsail parachutes. The geometric complexity created by the construction of the parachute from 'rings' and 'sails' with hundreds of gaps and slits makes this class of FSI modeling inherently challenging. There is still much room for advancing the computational technology for FSI modeling of a single raingsail parachute, such as improving the Homogenized Modeling of Geometric Porosity (HMGP) and developing special techniques for computing the reefed stages of the parachute and its disreefing. While we continue working on that, we are also developing special techniques targeting cluster modeling, so that the computational technology goes beyond the single parachute and the challenges specific to parachute clusters are addressed. The rotational-periodicity technique we describe here is one of such special techniques, and we use that for computing good starting conditions for FSI modeling of parachute clusters. In addition to reporting our preliminary FSI computations for parachute clusters, we present results from those starting-condition computations. In the category of more fundamental computational technologies, we discuss how we are improving the HMGP by increasing the resolution of the fluid mechanics mesh used in the HMGP computation and also by increasing the number of gores used. Also in that category, we describe how we use the multiscale sequentially coupled FSI techniques to improve the accuracy in computing the structural stresses in parts of the structure where we want to report more accurate values. All these special techniques are used in conjunction with the Stabilized Space-Time Fluid-Structure Interaction (SSTFSI) technique. Therefore, we also present in this paper a brief stability and accuracy analysis for the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, which is the core numerical technology of the SSTFSI technique. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Fluid-structure interaction modeling and performance analysis of the Orion spacecraft parachutes

    Takizawa, Kenji, Moorman, Creighton, Wright, Samuel, Spielman, Timothy, Tezduyar, Tayfun E.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 271 - 285  2011年01月  [査読有り]

     概要を見る

    We focus on fluid-structure interaction (FSI) modeling and performance analysis of the ringsail parachutes to be used with the Orion spacecraft. We address the computational challenges with the latest techniques developed by the T star AFSM (Team for Advanced Flow Simulation and Modeling) in conjunction with the SSTFSI (Stabilized Space-Time Fluid-Structure Interaction) technique. The challenges involved in FSI modeling include the geometric porosity of the ringsail parachutes with ring gaps and sail slits. We investigate the performance of three possible design configurations of the parachute canopy. We also describe the techniques developed recently for building a consistent starting condition for the FSI computations, discuss rotational periodicity techniques for improving the geometric-porosity modeling, and introduce a new version of the HMGP (Homogenized Modeling of Geometric Porosity). Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • COMPARATIVE PATIENT-SPECIFIC FSI MODELING OF CEREBRAL ANEURYSMS

    Takizawa, Kenji, Brummer, Tyler, Tezduyar, Tayfun E., Chen, Peng R.

    COMPUTATIONAL METHODS FOR COUPLED PROBLEMS IN SCIENCE AND ENGINEERING IV     590 - 599  2011年  [査読有り]

     概要を見る

    We consider a total of ten cases, at three different locations, half of which ruptured sometime after the images were taken. We use the stabilized space time FSI technique developed by the Team for Advanced Flow Simulation and Modeling, together with a number of special techniques targeting arterial FSI modeling. We compare the ten cases based on the wall shear stress, oscillatory shear index, and the arterial-wall stress. We also investigate how simpler approaches to computer modeling of cerebral aneurysms perform compared to FSI modeling.

  • Advances in computational fluid mechanics and fluid-structure interactions A tribute to Yoichiro Matsumoto on the occasion of his 60th birthday

    Tayfun E. Tezduyar, Yuri Bazilevs

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 1 - 2  2011年01月  [査読有り]

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  • 3D simulation of wind turbine rotors at full scale. Part I: Geometry modeling and aerodynamics

    Y. Bazilevs, M. -C. Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   65 ( 1-3 ) 207 - 235  2011年01月  [査読有り]

     概要を見る

    In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2 we focus on the structural discretization for wind turbine blades and the details of the fluid-structure interaction computational procedures. The methods developed are applied to the simulation of the NREL 5MW offshore baseline wind turbine rotor. The simulations are performed at realistic wind velocity and rotor speed conditions and at full spatial scale. Validation against published data is presented and possibilities of the newly developed computational framework are illustrated on several examples. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Space-time finite element computation of complex fluid-structure interactions

    Tezduyar, Tayfun E., Takizawa, Kenji, Moorman, Creighton, Wright, Samuel, Christopher, Jason

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   64 ( 10-12 ) 1201 - 1218  2010年12月  [査読有り]

     概要を見る

    New special fluid-structure interaction (FSI) techniques, supplementing the ones developed earlier, are employed with the Stabilized Space-Time FSI (SSTFSI) technique. The new special techniques include improved ways of calculating the equivalent fabric porosity in Homogenized Modeling of Geometric Porosity (HMGP), improved ways of building a starting point in FSI computations, ways of accounting for fluid forces acting on structural components that are not expected to influence the flow, adaptive HMGP, and multiscale sequentially coupled FSI techniques. While FSI modeling of complex parachutes was the motivation behind developing some of these techniques, they are also applicable to other classes of complex FSI problems. We also present new ideas to increase the scope of our FSI and CFD techniques. Copyright (C) 2009 John Wiley & Sons, Ltd.

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  • Space-time SUPG formulation of the shallow-water equations

    Shinsuke Takase, Kazuo Kashiyama, Seizo Tanaka, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   64 ( 10-12 ) 1379 - 1394  2010年12月  [査読有り]

     概要を見る

    We present a new space-time SUPG formulation of the shallow-water equations. In this formulation, we use a stabilization parameter that was introduced for compressible flows and a new shock-capturing parameter. In the context of two test problems, we evaluate the performance of the new shock-capturing parameter. We also evaluate the performance of the space-time SUPG formulation compared to the semi-discrete SUPG formulation, where the system of semi-discrete equations is solved with the central-difference (Crank-Nicolson) time-integration algorithm. Copyright (C) 2010 John Wiley & Sons, Ltd.

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  • Fifteenth international conference on finite elements in flow problems

    Kazuo Kashiyama, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   64 ( 10-12 ) 1064 - 1064  2010年12月  [査読有り]

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  • Wall shear stress calculations in space-time finite element computation of arterial fluid-structure interactions

    Takizawa, Kenji, Moorman, Creighton, Wright, Samuel, Christopher, Jason, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   46 ( 1 ) 31 - 41  2010年06月  [査読有り]

     概要を見る

    The stabilized space-time fluid-structure interaction (SSTFSI) technique was applied to arterial FSI problems soon after its development by the Team for Advanced Flow Simulation and Modeling. The SSTFSI technique is based on the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation and is supplemented with a number of special techniques developed for arterial FSI. The special techniques developed in the recent past include a recipe for pre-FSI computations that improve the convergence of the FSI computations, using an estimated zero-pressure arterial geometry, Sequentially Coupled Arterial FSI technique, using layers of refined fluid mechanics mesh near the arterial walls, and a special mapping technique for specifying the velocity profile at inflow boundaries with non-circular shape. In this paper we introduce some additional special techniques, related to the projection of fluid-structure interface stresses, calculation of the wall shear stress (WSS), and calculation of the oscillatory shear index. In the test computations reported here, we focus on WSS calculations in FSI modeling of a patient-specific middle cerebral artery segment with aneurysm. Two different structural mechanics meshes and three different fluid mechanics meshes are tested to investigate the influence of mesh refinement on the WSS calculations.

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  • Stabilized Methods for Compressible Flows

    Thomas J. R. Hughes, Guglielmo Scovazzi, Tayfun E. Tezduyar

    JOURNAL OF SCIENTIFIC COMPUTING   43 ( 3 ) 343 - 368  2010年06月  [査読有り]

     概要を見る

    This article reviews 25 years of research of the authors and their collaborators on stabilized methods for compressible flow computations. An historical perspective is adopted to document the main advances from the initial developments to modern approaches.

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  • Solution of linear systems in arterial fluid mechanics computations with boundary layer mesh refinement

    Manguoglu, Murat, Takizawa, Kenji, Sameh, Ahmed H., Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS   46 ( 1 ) 83 - 89  2010年06月  [査読有り]

     概要を見る

    Computation of incompressible flows in arterial fluid mechanics, especially because it involves fluid-structure interaction, poses significant numerical challenges. Iterative solution of the fluid mechanics part of the equation systems involved is one of those challenges, and we address that in this paper, with the added complication of having boundary layer mesh refinement with thin layers of elements near the arterial wall. As test case, we use matrix data from stabilized finite element computation of a bifurcating middle cerebral artery segment with aneurysm. It is well known that solving linear systems that arise in incompressible flow computations consume most of the time required by such simulations. For solving these large sparse nonsymmetric systems, we present effective preconditioning techniques appropriate for different stages of the computation over a cardiac cycle.

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  • Role of 0D peripheral vasculature model in fluid-structure interaction modeling of aneurysms

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   46 ( 1 ) 43 - 52  2010年06月  [査読有り]

     概要を見る

    Patient-specific simulations based on medical images such as CT and MRI offer information on the hemodynamic and wall tissue stress in patient-specific aneurysm configurations. These are considered important in predicting the rupture risk for individual aneurysms but are not possible to measure directly. In this paper, fluid-structure interaction (FSI) analyses of a cerebral aneurysm at the middle cerebral artery (MCA) bifurcation are presented. A 0D structural recursive tree model of the peripheral vasculature is incorporated and its impedance is coupled with the 3D FSI model to compute the outflow through the two branches accurately. The results are compared with FSI simulation with prescribed pressure variation at the outlets. The comparison shows that the pressure at the two outlets are nearly identical even with the peripheral vasculature model and the flow division to the two branches is nearly the same as what we see in the simulation without the peripheral vasculature model. This suggests that the role of the peripheral vasculature in FSI modeling of the MCA aneurysm is not significant.

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  • Multiscale sequentially-coupled arterial FSI technique

    Tezduyar, Tayfun E., Takizawa, Kenji, Moorman, Creighton, Wright, Samuel, Christopher, Jason

    COMPUTATIONAL MECHANICS   46 ( 1 ) 17 - 29  2010年06月  [査読有り]

     概要を見る

    Multiscale versions of the Sequentially-Coupled Arterial Fluid-Structure Interaction (SCAFSI) technique are presented. The SCAFSI technique was introduced as an approximate FSI approach in arterial fluid mechanics. It is based on the assumption that the arterial deformation during a cardiac cycle is driven mostly by the blood pressure. First we compute a "reference" arterial deformation as a function of time, driven only by the blood pressure profile of the cardiac cycle. Then we compute a sequence of updates involving mesh motion, fluid dynamics calculations, and recomputing the arterial deformation. The SCAFSI technique was developed and tested in conjunction with the stabilized space-time FSI (SSTFSI) technique. Beyond providing a computationally more economical alternative to the fully coupled arterial FSI approach, the SCAFSI technique brings additional flexibility, such as being able to carry out the computations in a spatially or temporally multiscale fashion. In the test computations reported here for the spatially multiscale versions of the SCAFSI technique, we focus on a patient-specific middle cerebral artery segment with aneurysm, where the arterial geometry is based on computed tomography images. The arterial structure is modeled with the continuum element made of hyperelastic (Fung) material.

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  • A tribute to Thomas JR Hughes on the occasion of his 65th birthday

    Arif Masud, Yuri Bazilevs, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   46 ( 1 ) 1 - 2  2010年06月  [査読有り]

    DOI

  • A DRD finite element formulation for computing turbulent reacting flows in gas turbine combustors

    A. Corsini, C. Iossa, F. Rispoli, T. E. Tezduyar

    COMPUTATIONAL MECHANICS   46 ( 1 ) 159 - 167  2010年06月  [査読有り]

     概要を見る

    An effective multiscale treatment of turbulent reacting flows is presented with the use of a stabilized finite element formulation. The method proposed is developed based on the streamline-upwind/Petrov-Galerkin (SUPG) formulation, and includes discontinuity capturing in the form of a new generation "DRD" method, namely the "DRDJ" technique. The stabilized formulation is applied to finite-rate chemistry modelling based on mixture-fraction approaches with the so-called presumed-PDF technique. The turbulent combustion process is simulated for an aero-engine combustor configuration of RQL concept in non-premixed flame regime. The comparative analysis of the temperature and velocity fields demonstrate that the proposed SUPG+DRDJ formulation outperforms the stand-alone SUPG method. The improved accuracy is demonstrated in terms of the combustor overall performance, and the mechanisms involved in the distribution of the numerical diffusivity are also discussed.

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  • Influence of wall thickness on fluid-structure interaction computations of cerebral aneurysms

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING   26 ( 3-4 ) 336 - 347  2010年03月  [査読有り]

     概要を見る

    Fluid structure interaction (FSI) analyses of cerebral aneurysm using patient-specific geometry with uniform and pathological aneurysmal wall thickness models are carried out. The objective is to assess the influence of the wall thickness on the FSI and hemodynamics in aneurysms. Two aneurysm models that were reconstructured based on CT images are used. The arterial wall thickness is set to 0.3 mm for the non-aneurysmal artery and to 0.05 mm for the aneurysmal wall based on experimental findings. Another set of aneurysm models with a uniform wall thickness of 0.3 mm for the entire model is used for comparison. The FSI simulations are carried out using the deforming-spatial-domain/stabilized space time method with physiological inflow and pressure profiles. Computations with different aneurysmal wall thicknesses depict considerable differences in displacement, flow velocity and wall shear stress (WSS). The wall displacement for the pathological wall model is 61% larger than that of the uniform wall model. Consequently, the flow velocities in the aneurysm with the pathological wall model are lower, and that results in a 51% reduction in WSS on the aneurismal wall. Because low WSS on the aneurymal wall is linked to growth and rupture risk of aneurysm, the results suggest that using uniform wall thickness for the aneurysmal wall could underestimate risk in aneurysms. Copyright (C) 2009 John Wiley & Sons, Ltd.

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  • Space-time finite element computation of arterial fluid-structure interactions with patient-specific data

    Takizawa, Kenji, Christopher, Jason, Tezduyar, Tayfun E., Sathe, Sunil

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING   26 ( 1 ) 101 - 116  2010年01月  [査読有り]

     概要を見る

    The stabilized space time fluid structure interaction (SSTFSI) technique developed by the team for advanced flow simulation and modeling is applied to the computation of arterial fluid structure interaction (FSI) with patient-specific data. The SSTFSI technique is based on the deforming-spatial-domain/stabilized space time formulation and is supplemented with a number of special techniques developed for arterial FSI. These include a recipe for pre-FSI computations that improve the convergence of the FSI computations, using an estimated zero-pressure arterial geometry, layers of refined fluid mechanics mesh near the arterial walls, and a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape. In the test computations reported here, we focus on a patient-specific middle cerebral artery segment with aneurysm, where the arterial geometry is based on computed tomography images. Copyright (C) 2009 John Wiley & Sons, Ltd.

    DOI

  • Improving stability of stabilized and multiscale formulations in flow simulations at small time steps

    M. -C. Hsu, Y. Bazilevs, V. M. Calo, T. E. Tezduyar, T. J. R. Hughes

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   199 ( 13-16 ) 828 - 840  2010年  [査読有り]

     概要を見る

    The objective of this paper is to show that use of the element-vector-based definition of stabilization parameters, introduced in [T.E. Tezduyar, Computation of moving boundaries and interfaces and stabilization parameters, Int. J. Numer. Methods Fluids 43 (2003) 555-575: T.E. Tezduyar, Y. Osawa, Finite element stabilization parameters computed from element matrices and vectors, Comput. Methods Appl. Mech. Engrg. 190 (2000) 411-430], circumvents the well-known instability associated with conventional stabilized formulations at small time steps. We describe formulations for linear advection-diffusion and incompressible Navier-Stokes equations and test them on three benchmark problems: advection of an L-shaped discontinuity, laminar flow in a square domain at low Reynolds number, and turbulent channel flow at friction-velocity Reynolds number of 395. (C) 2009 Elsevier B.V. All rights reserved.

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  • Computer modeling and analysis of the Orion spacecraft parachutes

    Takizawa K, Moorman C, Wright S, Tezduyar T.E

    Lecture Notes in Computational Science and Engineering   73 LNCSE   53 - 81  2010年  [査読有り]

    DOI

  • Correct implementation of the fluid-object interactions subcomputation technique (FOIST)

    Tayfun E. Tezduyar

    COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING   25 ( 10 ) 1055 - 1058  2009年10月  [査読有り]

     概要を見る

    Full understanding of the fluid-object interactions subcomputation technique (FOIST) and the related fundamental concepts in dynamics and fluid mechanics is essential in using this technique in a meaningful way. We explain what constitutes a correct implementation of the FOIST and give a published example of what does not. Copyright (C) 2009 John Wiley & Sons, Ltd.

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  • Comments on 'Simplex space-time meshes in finite element simulations'

    Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   60 ( 11 ) 1289 - 1290  2009年08月  [査読有り]

     概要を見る

    Some comments are provided on the citations offered in a recent paper (M. Behr, Int. J. Numer Meth. Fluids 2008; 57:1421-1434) that describes space-time finite element computations of advection of 'Gaussian hills', including computations with mesh refinement in the time direction. Copyright (C) 2008 John Wiley & Sons, Ltd.

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  • Three-Dimensional Edge-Based SUPG Computation of Inviscid Compressible Flows With YZ beta Shock-Capturing

    Lucia Catabriga, Denis A. F. de Souza, Alvaro L. G. A. Coutinho, Tayfun E. Tezduyar

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 1 - 7  2009年03月  [査読有り]

     概要を見る

    The streamline-upwind/Petrov-Galerkin (SUPG) formulation of compressible flows based on conservation variables, supplemented with shock-capturing, has been successfully used over a quarter of a century. In this paper, for inviscid compressible flows, the YZ beta shock-capturing parameter, which was developed recently and is based on conservation variables only, is compared with an earlier parameter derived based on the entropy variables. Our studies include comparing, in the context of these two versions of the SUPG formulation, computational efficiency of the element- and edge-based data structures in iterative computation of compressible flows. Tests include 1D, 2D, and 3D examples. [DOI: 10.1115/1.3062968]

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  • Special Issue on Stabilized, Multiscale, and Multiphysics Methods in Fluid Mechanics

    Arif Masud, Tayfun E. Tezduyar, Yoichiro Matsumoto

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 20601 - 1  2009年03月  [査読有り]

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  • Preconditioning Techniques for Nonsymmetric Linear Systems in the Computation of Incompressible Flows

    Murat Manguoglu, Ahmed H. Sameh, Faisal Saied, Tayfun E. Tezduyar, Sunil Sathe

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 1 - 7  2009年03月  [査読有り]

     概要を見る

    In this paper we present effective preconditioning techniques for solving the nonsymmetric systems that arise from the discretization of the Navier-Stokes equations. These linear systems are solved using either Krylov subspace methods or the Richardson scheme. We demonstrate the effectiveness of our techniques in handling time-accurate as well as steady-state solutions. We also compare our solvers with those published previously. [DOI: 10.1115/1.3059576]

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  • Computational Modeling of the Collapse of a Liquid Column Over an Obstacle and Experimental Validation

    Marcela A. Cruchaga, Diego J. Celentano, Tayfun E. Tezduyar

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 1 - 5  2009年03月  [査読有り]

     概要を見る

    We present the numerical and experimental analyses of the collapse of a water column over an obstacle. The physical model consists of a water column initially confined by a closed gate inside a glass box. An obstacle is placed between the gate and the right wall of the box, inside the initially unfilled zone. Once the gate is opened, the liquid spreads in the container and over the obstacle. Measurements of the liquid height along the walls and a middle control section are obtained from videos. The computational modeling is carried out using a moving interface technique, namely, the edge-tracked interface locator technique, to calculate the evolution of the water-air interface. The analysis involves a water-column aspect ratio of 2, with different obstacle geometries. The numerical predictions agree reasonably well with the experimental trends. [DOI: 10.1115/1.3057439]

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  • Computation of Inviscid Supersonic Flows Around Cylinders and Spheres With the V-SGS Stabilization and YZ beta Shock-Capturing

    Franco Rispoli, Rafael Saavedra, Filippo Menichini, Tayfun E. Tezduyar

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 1 - 6  2009年03月  [査読有り]

     概要を見る

    The YZ beta shock-capturing technique was introduced originally for use in combination with the streamline-upwind/Petrov-Galerkin (SUPG) formulation of compressible flows in conservation variables. It is a simple residual-based shock-capturing technique. Later it was also combined with the variable subgrid scale (V-SGS) formulation of compressible flows in conservation variables and tested on standard 2D test problems. The V-SGS method is based on an approximation of the class of SGS models derived from the Hughes variational multiscale method. In this paper, we carry out numerical experiments with inviscid supersonic flows around cylinders and spheres to evaluate the performance of the YZ beta shock-capturing combined with the V-SGS method. The cylinder computations are carried out at Mach numbers 3 and 8, and the sphere computations are carried out at Mach number 3. The results compare well to those obtained with the YZ beta shock-capturing combined with the SUPG formulation, which were shown earlier to compare very favorably to those obtained with the well established OVERFLOW code. [DOI: 10.1115/1.3057496]

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  • A Multiscale Finite Element Formulation With Discontinuity Capturing for Turbulence Models With Dominant Reactionlike Terms

    A. Corsini, F. Menichini, F. Rispoli, A. Santoriello, T. E. Tezduyar

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   76 ( 2 ) 1 - 8  2009年03月  [査読有り]

     概要を見る

    A stabilization technique targeting the Reynolds-averaged Navier-Stokes (RANS) equations is proposed to account for the multiscale nature of turbulence and high solution gradients. The objective is effective stabilization in computations with the advection-diffusion reaction equations, which are typical of the class of turbulence scale-determining equations where reaction-dominated effects strongly influence the boundary layer prediction in the presence of nonequilibrium phenomena. The stabilization technique, which is based on a variational multiscale method, includes a discontinuity-capturing term designed to be operative when the solution gradients are high and the reactionlike terms are dominant. As test problems, we use a 2D model problem and 3D flow computation for a linear compressor cascade. [DOI: 10.1115/1.3062967]

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  • Sequentially-Coupled Arterial Fluid-Structure Interaction (SCAFSI) technique

    Tayfun E. Tezduyar, Matthew Schwaab, Sunil Sathe

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   198 ( 45-46 ) 3524 - 3533  2009年  [査読有り]

     概要を見る

    The Sequentially-Coupled Arterial Fluid-Structure Interaction (SCAFSI) technique is one of the special techniques developed recently by the Team for Advanced Flow Simulation and Modeling (T*AFSM) for FSI modeling of blood flow and arterial dynamics. The SCAFSI technique, which was introduced as an approximate FSI approach in arterial fluid mechanics, is based on the assumption that the arterial deformation during a cardiac cycle is driven mostly by the blood pressure. In the SCAFSI, first we compute a "reference" arterial deformation as a function of time, driven only by the blood pressure profile of the cardiac cycle. Then we compute a sequence of updates involving mesh motion, fluid dynamics calculations, and recomputing the arterial deformation. Although the SCAFSI technique was developed and tested in conjunction with the stabilized space-time FSI (SSTFSI) technique, it can also be used in conjunction with other FSI modeling techniques categorized as moving-mesh methods. The SSTFSI technique is based on the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation and includes the enhancements introduced recently by the T*AFSM. The arterial structures can be modeled with the membrane or continuum elements, both of which are geometrically nonlinear, and the continuum element can be made of linearly-elastic or hyperelastic material (Mooney-Riviin or Fung). Here we provide an overview of the SCAFSI technique and present a number of test computations for abdominal aortic and cerebral aneurysms, where the arterial geometries used in the computations are close approximations to the patient-specific image-based data. (C) 2008 Elsevier B.V. All rights reserved.

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  • Preface: Special issue on stabilized, multiscale, and multiphysics methods in fluid mechanics

    Masud A, Tezduyar T.E, Matsumoto Y

    Journal of Applied Mechanics, Transactions ASME   76 ( 2 )  2009年  [査読有り]

  • Fluid-structure interaction modeling of blood flow and cerebral aneurysm: Significance of artery and aneurysm shapes

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   198 ( 45-46 ) 3613 - 3621  2009年  [査読有り]

     概要を見る

    Because wall shear stress (WSS) is known to play an important role in initiation, growth and rupture of cerebral aneurysm, predicting the hemodynamic forces near the aneurysmal site helps with understanding aneurysms better. Earlier research reports indicate that the WSS around the aneurysmal site has a significant relationship with the vascular and aneurysm morphology. It was also shown statistically that the aneurysm shape (aspect ratio) is an indicator of rupture risk in cerebral aneurysm. In this study, fluid-structure interaction (FSI) modeling of a ruptured aneurysm, two unruptured aneurysms at the middle cerebral artery (MCA) bifurcation, and a MCA bifurcation without aneurysm is carried out using vascular geometries reconstructed from CT images. We use pulsatile boundary conditions based on a physiological flow velocity waveform and investigate the relationship between the hemodynamic forces and vascular morphology for different arteries and aneurysms. The results are compared with the results obtained for the rigid arterial wall to highlight the role of FSI in the patient-specific modeling of cerebral aneurysm. The results show that the interaction between the blood flow and arterial deformation alters the hemodynamic forces acting on the arterial wall and the interaction strongly depends on the individual aneurysm shapes. Flow impingement on the arterial wall plays a key role in determining the interaction and hemodynamic forces. When the blood flow impinges strongly on the wall, the maximum WSS tends to decrease due to the flow-wall interaction. When the blood flows straight into an aneurysm, the flow and the resulting WSS patterns are altered both qualitatively and quantitatively. When the blood in the aneurysm is nearly stagnant, a slow flow is induced by the wall motion, which raises the minimum WSS on the aneurysmal wall. The results reinforce the importance of FSI in patient-specific analysis of cerebral aneurysms. (C) 2008 Elsevier B.V. All rights reserved.

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  • Preface on the special issue on fluid-structure interaction

    Tayfun E. Tezduyar, Yuri Bazilevs

    COMPUTATIONAL MECHANICS   43 ( 1 ) 1 - 1  2008年12月  [査読有り]

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  • Modeling of fluid-structure interactions with the space-time finite elements: contact problems

    Sunil Sathe, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   43 ( 1 ) 51 - 60  2008年12月  [査読有り]

     概要を見る

    Fluid-structure interaction computations based on interface-tracking (moving-mesh) techniques are often hindered if the structural surfaces come in contact with each other. As the distance between two structural surfaces tends to zero, the fluid mesh in between distorts severely and eventually becomes invalid. Our objective is to develop a technique for modeling problems where the contacting structural surfaces would otherwise inhibit flow modeling or even fluid-mesh update. In this paper, we present our contact tracking technique that detects impending contact and maintains a minimum distance between the contacting structural surfaces. Our Surface-Edge-Node Contact Tracking (SENCT) technique conducts a topologically hierarchical search to detect contact between each node and the elements ("surfaces"), edges and other nodes. To keep the contacting surfaces apart by a small distance, we apply to the contacted nodes penalty forces in SENCT-Force (SENCT-F) and displacement restrictions in SENCT-Displacement (SENCT-D). By keeping a minimum distance between the contacting surfaces, we are able to update the fluid mesh in between and model the flow accurately.

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  • Interface projection techniques for fluid-structure interaction modeling with moving-mesh methods

    Tayfun E. Tezduyar, Sunil Sathe, Jason Pausewang, Matthew Schwaab, Jason Christopher, Jason Crabtree

    COMPUTATIONAL MECHANICS   43 ( 1 ) 39 - 49  2008年12月  [査読有り]

     概要を見る

    The stabilized space-time fluid-structure interaction (SSTFSI) technique developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM) was applied to a number of 3D examples, including arterial fluid mechanics and parachute aerodynamics. Here we focus on the interface projection techniques that were developed as supplementary methods targeting the computational challenges associated with the geometric complexities of the fluid-structure interface. Although these supplementary techniques were developed in conjunction with the SSTFSI method and in the context of air-fabric interactions, they can also be used in conjunction with other moving-mesh methods, such as the Arbitrary Lagrangian-Eulerian (ALE) method, and in the context of other classes of FSI applications. The supplementary techniques currently consist of using split nodal values for pressure at the edges of the fabric and incompatible meshes at the air-fabric interfaces, the FSI Geometric Smoothing Technique (FSI-GST), and the Homogenized Modeling of Geometric Porosity (HMGP). Using split nodal values for pressure at the edges and incompatible meshes at the interfaces stabilizes the structural response at the edges of the membrane used in modeling the fabric. With the FSI-GST, the fluid mechanics mesh is sheltered from the consequences of the geometric complexity of the structure. With the HMGP, we bypass the intractable complexities of the geometric porosity by approximating it with an "equivalent", locally-varying fabric porosity. As test cases demonstrating how the interface projection techniques work, we compute the air-fabric interactions of windsocks, sails and ringsail parachutes.

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  • Fluid-structure interaction modeling of ringsail parachutes

    Tayfun E. Tezduyar, Sunil Sathe, Matthew Schwaab, Jason Pausewang, Jason Christopher, Jason Crabtree

    COMPUTATIONAL MECHANICS   43 ( 1 ) 133 - 142  2008年12月  [査読有り]

     概要を見る

    In this paper, we focus on fluid-structure interaction (FSI) modeling of ringsail parachutes, where the geometric complexity created by the "rings" and "sails" used in the construction of the parachute canopy poses a significant computational challenge. It is expected that NASA will be using a cluster of three ringsail parachutes, referred to as the "mains", during the terminal descent of the Orion space vehicle. Our FSI modeling of ringsail parachutes is based on the stabilized space-time FSI (SSTFSI) technique and the interface projection techniques that address the computational challenges posed by the geometric complexities of the fluid-structure interface. Two of these interface projection techniques are the FSI Geometric Smoothing Technique and the Homogenized Modeling of Geometric Porosity. We describe the details of how we use these two supplementary techniques in FSI modeling of ringsail parachutes. In the simulations we report here, we consider a single main parachute, carrying one third of the total weight of the space vehicle. We present results from FSI modeling of offloading, which includes as a special case dropping the heat shield, and drifting under the influence of side winds.

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  • Fluid-structure interaction modeling of a patient-specific cerebral aneurysm: influence of structural modeling

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   43 ( 1 ) 151 - 159  2008年12月  [査読有り]

     概要を見る

    Fluid-structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on patient-specific FSI simulations. The maximum displacement computed with the hyper-elastic model is 36% smaller compared to the linearly elastic material model, but the displacement patterns such as the site of local maxima are not sensitive to the wall models. The blood near the apex of an aneurysm is likely to be stagnant, which causes very low wall shear stress and is a factor in rupture by degrading the aneurysmal wall. In this study, however, relatively high flow velocities due to the interaction between the blood flow and aneurysmal wall are seen to be independent of the wall model. The present results indicate that both linearly elastic and hyper-elastic models can be useful to investigate aneurysm FSI.

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  • A nested iterative scheme for computation of incompressible flows in long domains

    Murat Manguoglu, Ahmed H. Sameh, Tayfun E. Tezduyar, Sunil Sathe

    COMPUTATIONAL MECHANICS   43 ( 1 ) 73 - 80  2008年12月  [査読有り]

     概要を見る

    We present an effective preconditioning technique for solving the nonsymmetric linear systems encountered in computation of incompressible flows in long domains. The application category we focus on is arterial fluid mechanics. These linear systems are solved using a nested iterative scheme with an outer Richardson scheme and an inner iteration that is handled via a Krylov subspace method. Test computations that demonstrate the robustness of our nested scheme are presented.

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  • Stabilized formulations for incompressible flows with thermal coupling

    Tayfun E. Tezduyar, Srinivas Ramakrishnan, Sunil Sathe

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   57 ( 9 ) 1189 - 1209  2008年07月  [査読有り]

     概要を見る

    We present applications of the stabilized finite element formulations developed for incompressible flows with thermal coupling to 2D and 3D test problems. The stabilized formulations are based on the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin stabilizations and are supplemented with discontinuity capturing (DC), including the discontinuity-capturing directional dissipation. The stabilization and DC parameters associated with these formulations are also presented. The coupled fluid mechanics and temperature equations are solved with a direct coupling technique. The test problems computed include 2D and 3D natural convection, as well as a simplified 3D model of air Circulation in a small data center. Copyright (C) 2008 John Wiley & Sons, Ltd.

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  • Arterial fluid mechanics modeling with the stabilized space-time fluid-structure interaction technique

    Tayfun E. Tezduyar, Sunil Sathe, Matthew Schwaab, Brian S. Conklin

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   57 ( 5 ) 601 - 629  2008年06月  [査読有り]

     概要を見る

    We present an overview of how the arterial fluid mechanics problems can be modeled with the stabilized space-time fluid-structure interaction (SSTFSI) technique developed by the Team for Advanced Flow Simulation and Modeling (T(*)AFSM). The SSTFSI technique includes the enhancements introduced recently by the T(*)AFSM to increase the scope, accuracy, robustness and efficiency of this class of techniques. The SSTFSI technique is supplemented with a number of special techniques developed for arterial fluid mechanics modeling. These include a recipe for pre-FSI computations that improve the convergence of the FSI computations, using an estimated zero-pressure arterial geometry, and the sequentially coupled arterial FSI (SCAFSI) technique. The recipe for pre-FSI computations is based on the assumption that the arterial deformation during a cardiac cycle is driven mostly by the blood pressure. The SCAFSI technique, which was introduced as an approximate FSI approach in arterial fluid mechanics, is also based on that assumption. The need for an estimated zero-pressure arterial geometry is based on recognizing that the patient- specific image-based geometries-correspond to time-averaged blood pressure values. In our arterial fluid mechanics modeling the arterial walls can be represented with the membrane or continuum elements, both of which are geometrically nonlinear, and the continuum element is made of hyperelastic (Fung) material. Test computations are presented for cerebral and abdominal aortic aneurysms, where the arterial geometries used in the computations are close approximations to the patient-specific image-based data. Copyright (C) 2007 John Wiley & Sons, Ltd.

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  • "Parallel implementation of structural dynamic analysis for parachute simulation"

    Tayfun E. Tezduyar, E. Livne

    AIAA JOURNAL   45 ( 9 ) 2364 - 2364  2007年09月  [査読有り]

    DOI

  • YZ beta discontinuity capturing for advection-dominated processes with application to arterial drug delivery

    Y. Bazilevs, V. M. Calo, T. E. Tezduyar, T. J. R. Hughes

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 593 - 608  2007年06月  [査読有り]

     概要を見る

    The YZ beta discontinuity-capturing operator, recently introduced in (Encyclopedia of Computational Mechanics, Vol. 3, Fluids. Wiley: New York, 2004) in the context of compressible flows, is applied to a time-dependent, scalar advection-diffusion equation with the purpose of modelling drug delivery processes in blood vessels. The formulation is recast in a residual-based form, which reduces to the previously proposed formulation in the limit of zero diffusion and source term. The NURBS-based isogeometric analysis method, proposed by Hughes et al. (Comput. Methods Appl. Mech. Eng. 2005; 194:4135-4195) was used for the numerical tests. Effects of various parameters in the definition of the YZ beta operator are examined on a model problem and the better performer is singled out. While for low-order B-spline functions discontinuity capturing is necessary to improve solution quality, we find that high-order, high-continuity B-spline discretizations produce sharp, nearly monotone layers without the aid of discontinuity capturing. Finally, we successfully apply the YZ beta approach to the simulation of drug delivery in patient-specific coronary arteries. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Ship hydrodynamics computations with the CIP method based on adaptive Soroban grids

    Takizawa, Kenji, Tanizawa, Katsuji, Yabe, Takashi, Tezduyar, Tayfun E.

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 1011 - 1019  2007年06月  [査読有り]

     概要を見る

    The constrained interpolation profile/cubic interpolated pseudo-particle (CIP) combined unified procedure (CCUP) method (J Phys. Soc. Jpn. 1991; 60:2105-2108), which is based on the CIP method (J. Comput. Phys. 1985: 61:261-268; J Comput. Phys. 1987; 70:355-372; Comput. Phys. Commun. 1991; 66:219-232; J Comput. Phys. 2001; 169:556-593) and the adaptive Soroban grid technique (J. Comput. Phys. 2004; 194:55-77) were combined in (Comput. Mech. 2006; published online) for computation of 3D fluid-object and fluid-structure interactions in the presence of free surfaces and fluid-fluid interfaces. Although the grid system is unstructured, it still has a very simple data structure and this facilitates computational efficiency. Despite the unstructured and collocated features of the grid, the method maintains high-order accuracy and Computational robustness. Furthermore, the meshless feature of the combined technique brings freedom from mesh moving and distortion issues. In this paper, the combined technique is extended to ship hydrodynamics computations. We introduce a new way of computing the advective terms to increase the efficiency in that part of the computations. This is essential in ship hydrodynamics computations where the level of grid refinement needed near the ship Surface and at the free surface results in very large grid sizes. The test cases presented are a test computation with a wave-making wedge and simulation of the hydrodynamics of a container ship. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Numerical investigation of the effect of hypertensive blood pressure on cerebral aneurysm - Dependence of the effect on the aneurysm shape

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 995 - 1009  2007年06月  [査読有り]

     概要を見る

    Fluid-structure interaction (FSI) computations of two cerebral aneurysms are carried out under hypertensive and normotensive blood pressures. Hypertensive blood pressure is one of the major risk factors in subarachnoid hemorrhage which is mostly caused by the rupture of cerebral aneurysm. Since hemodynamic wall shear stress (WSS) is known to play an important role in aneurysm progression, investigating the WSS distribution in conjunction with hypertensive blood pressure is expected to provide a better understanding of aneurysms. The WSS distributions obtained front the simulations show that hypertensive blood pressure considerably affects one of the Subjects but not the other. The effect is a wider spreading of the high WSS region on the aneurysm wall, which prevents the wall from weakening. It is also shown that the deformation of the aneurysm wall can alter the flow patterns in the aneurysm to diminish the stagnant flow near the apex. which is linked to the weakening of the wall. The effect of hypertensive blood pressure and wall deformation is shown to be highly de pendent on individual aneurysm geometry, and that stresses the importance of subject-specific simulations. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Modelling of fluid-structure interactions with the space-time finite elements: Solution techniques

    Tayfun E. Tezduyar, Sunil Sathe

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 855 - 900  2007年06月  [査読有り]

     概要を見る

    The space-time fluid-structure interaction (FSI) techniques developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM) have been applied to a wide range of 3D computation of FSI problems. some as early as in 1994 and many with challenging complexities. In this paper, we review these space-time FSI techniques and describe the enhancements introduced recently by the T*AFSM to increase the scope. accuracy, robustness and efficiency of these techniques. The aspects of the FSI solution process enhanced include the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, the fluid-structure interface conditions, the preconditioning techniques used in iterative solution of the linear equation systems, and a contact algorithm protecting the quality of the fluid mechanics mesh between the structural surfaces coming into contact. We present a number of 3D numerical examples computed with these new stabilized space-time FSI (SSTFSI) techniques. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Modelling of fluid-structure interactions with the space-time finite elements: Arterial fluid mechanics

    Tayfun E. Tezduyar, Sunil Sathe, Timothy Cragin, Bryan Nanna, Brian S. Conklin, Jason Pausewang, Matthew Schwaab

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 901 - 922  2007年06月  [査読有り]

     概要を見る

    The stabilized space-time fluid-structure interaction (SSTFSI) techniques developed by the Team for Advanced How Simulation and Modeling (T*AFSM) are applied to FSI modelling in arterial fluid mechanics. Modelling of flow in arteries with aneurysm is emphasized. The SSTFSI techniques used are based on the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation and include the enhancements introduced recently by the T*AFSM to increase the scope, accuracy, robustness and efficiency of these techniques. The arterial structures can be modelled with the membrane or continuum elements, both of which are geometrically nonlinear, and the continuum element can be made of linearly elastic or hyperelastic material. Test computations are presented for cerebral and abdominal aortic aneurysms and carotid-artery bifurcation, where the arterial geometries used in the computations are close approximations to the patient-specific image-based data. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Computation of inviscid compressible flows with the V-SGS stabilization and YZ beta shock-capturing

    Franco Rispoli, Rafael Saavedra, Alessandro Corsini, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 695 - 706  2007年06月  [査読有り]

     概要を見る

    The YZ beta shock-capturing technique was introduced recently for use in combination with the streandine-upwind/Petrov-Galerkin formulation of compressible flows in conservation variables. The YZ beta shock-capturing parameter is much simpler than an earlier parameter derived from the entropy variables for use in conservation variables. In this paper, we propose to use the YZ beta shock-capturing in combination with the variable subgrid scale (V-SGS) formulation of compressible flows in conservation variables. The V-SGS method is based on an approximation of the class of SGS models derived from the Hughes variational multiscale method. We evaluate the performance of the V-SGS and YZ beta combination in a number of standard, 2D test problems. Compared to the earlier shock-capturing parameter derived from the entropy variables, in addition to being much simpler, the YZ beta shock-capturing parameter yields better shock quality in these test problems. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Computation of free-surface flows and fluid-object interactions with the CIP method based on adaptive meshless soroban grids

    Takizawa, Kenji, Yabe, Takashi, Tsugawa, Yumiko, Tezduyar, Tayfun E., Mizoe, Hiroki

    COMPUTATIONAL MECHANICS   40 ( 1 ) 167 - 183  2007年06月  [査読有り]

     概要を見る

    The CIP Method [J comput phys 61:261-268 1985; J comput phys 70:355-372, 1987; Comput phys commun 66:219-232 1991; J comput phys 169:556-593, 2001] and adaptive Soroban grid [J comput phys 194:57-77, 2004] are combined for computation of three- dimensional fluid-object and fluid-structure interactions, while maintaining high-order accuracy. For the robust computation of free-surface and multi-fluid flows, we adopt the CCUP method [Phys Soc Japan J 60:2105-2108 1991]. In most of the earlier computations, the CCUP method was used with a staggered-grid approach. Here, because of the meshless nature of the Soroban grid, we use the CCUP method with a collocated-grid approach. We propose an algorithm that is stable, robust and accurate even with such collocated grids. By adopting the CIP interpolation, the accuracy is largely enhanced compared to linear interpolation. Although this grid system is unstructured, it still has a very simple data structure.

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  • Computation of fluid-solid and fluid-fluid interfaces with the CIP method based on adaptive Soroban grids - An overview

    Yabe, Takashi, Takizawa, Kenji, Tezduyar, Tayfun E., Im, Hyo-Nam

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 841 - 853  2007年06月  [査読有り]

     概要を見る

    We provide an overview of how fluid-solid and fluid-fluid interfaces can be computed successfully with the constrained interpolation profile/cubic interpolated pseudo-particle (CIP) method (J. Comput. Phys. 1985; 61:261-268; Comput. Phys. Commun. 1991; 66:219-232; Comput. Phys. Commun. 1991; 66: 23j-242: J. Comput. Phys. 2001; 169:556-593) based on adaptive Soroban grids (J. Comput. Phys. 2004; 194:57-77). In this approach, the CIP combined unified procedure (CCUP) technique (J. Phys. Soc. Jpn 1991; 60:2105-2108), which is based on the CIP method, is combined with the adaptive Soroban and technique. One of the superior features of the approach is that even though the grid system is unstructured, it still has a simple data structure that renders remarkable computational efficiency. Another superior feature is that despite the unstructured and collocated nature of the grid, high-order accuracy and computational robustness are maintained. In addition, because the Soroban grid technique does not have any elements or cells connecting the grid points, the approach does not involve mesh distortion limitations. While the details of the approach and several numerical examples were reported in (Comput. Mech. 2006: published online), our objective in this paper is to provide an easy-to-follow description of the key aspects of the approach. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • A Numerical model based on the mixed interface-tracking/interface-capturing technique (MITICT) for flows with fluid-solid and fluid-fluid interfaces

    Marcela A. Cruchaga, Diego J. Celentano, Tayfun E. Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   54 ( 6-8 ) 1021 - 1030  2007年06月  [査読有り]

     概要を見る

    We propose a numerical model for computation of flow problems that involve both fluid-solid and fluid-fluid interfaces. The model is based on the mixed interface-tracking/interface-capturing technique (MITICT), which was introduced earlier for problems that involve both fluid-solid interfaces that are accurately tracked with a moving mesh method and fluid-fluid interfaces that are too complex to track and therefore treated with an interface-capturing technique. In our numerical model, fluid-solid interfaces are handled with the moving Lagrangian interface technique (MLIT) and fluid-fluid interfaces with the edge-tracked interface locator technique (ETILT). The mixed technique is tested in computation of a fluid-particle interaction problem in the presence of a fluid-fluid interface impacted by the particle. Copyright (c) 2007 John Wiley & Sons, Ltd.

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  • Collapse of a liquid column: numerical simulation and experimental validation

    Marcela A. Cruchaga, Diego J. Celentano, Tayfun E. Tezduyar

    COMPUTATIONAL MECHANICS   39 ( 4 ) 453 - 476  2007年03月  [査読有り]

     概要を見る

    This paper is focused on the numerical and experimental analyses of the collapse of a liquid column. The measurements of the interface position in a set of experiments carried out with shampoo and water for two different initial column aspect ratios are presented together with the corresponding numerical predictions. The experimental procedure was found to provide acceptable recurrence in the observation of the interface evolution. Basic models describing some of the relevant physical aspects, e. g. wall friction and turbulence, are included in the simulations. Numerical experiments are conducted to evaluate the influence of the parameters involved in the modeling by comparing the results with the data from the measurements. The numerical predictions reasonably describe the physical trends.

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  • Finite elements in fluids: Stabilized formulations and moving boundaries and interfaces

    Tayfun E. Tezduyar

    COMPUTERS & FLUIDS   36 ( 2 ) 191 - 206  2007年02月  [査読有り]

     概要を見る

    We provide an overview of the finite element methods we developed for fluid dynamics problems. We focus on stabilized formulations and moving boundaries and interfaces. The stabilized formulations are the streamline-upwind/Petrov-Galerkin (SUPG) formulations for compressible and incompressible flows and the pressure-stabilizing/Petrov-Galerkin (PSPG) formulation for incompressible flows. These are supplemented with the discontinuity-capturing directional dissipation (DCDD) for incompressible flows and the shock-capturing terms for compressible flows. Determination of the stabilization and shock-capturing parameters used in these formulations is highlighted. Moving boundaries and interfaces include free surfaces, two-fluid interfaces, fluid-object and fluid-structure interactions, and moving mechanical components. The methods developed for this class of problems can be classified into two main categories: interface-tracking and interface-capturing techniques. The interface-tracking techniques are based on the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, where the mesh moves to track the interface. The interface-capturing techniques were developed for two-fluid flows. They are based on the stabilized formulation, over typically non-moving meshes, of both the flow equations and an advection equation. The advection equation governs the time-evolution of an interface function marking the interface location. We also describe some of the additional methods and ideas we introduced to increase the scope and accuracy of these two classes of techniques. Among them is the enhanced-discretization interface-capturing technique (EDICT), which was developed to increase the accuracy in capturing the interface. Also among them is the mixed interface-tracking/interface-capturing technique (MITICT), which was introduced for problems that involve both interfaces that can be accurately tracked with a moving-mesh method and interfaces that call for an interface-capturing technique. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Finite elements in fluids: Special methods and enhanced solution techniques

    Tayfun E. Tezduyar

    COMPUTERS & FLUIDS   36 ( 2 ) 207 - 223  2007年02月  [査読有り]

     概要を見る

    As a sequel to "Finite elements in fluids: stabilized formulations and moving boundaries and interfaces" [Tezduyar TE. Finite elements in fluids: stabilized formulations and moving boundaries and interfaces. Comput Fluids, in press, doi:10.1016/j.compfluid. 2005.02.011.]. in this article we provide an overview of the special methods and enhanced solution techniques we developed in conjunction with the methods described in the accompanying paper. The methods and ideas highlighted here were introduced to increase the scope and accuracy of the stabilized formulations and interface-tracking and interface-capturing techniques highlighted in the accompanying paper. They include special methods for fluid-object interactions, for flows involving objects in fast, linear or rotational relative motion, and for two-fluid flows. They also include enhanced solutions techniques, where we have enhancement in spatial discretization, enhancement in time discretization, and enhancement in iterative solution of non-linear and linear equation systems. (c) 2005 Elsevier Ltd. All rights reserved.

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  • SUPG finite element computation of inviscid supersonic flows with YZ beta shock-Capturing

    Tayfun E. Tezduyar, Masayoshi Senga

    COMPUTERS & FLUIDS   36 ( 1 ) 147 - 159  2007年01月  [査読有り]

     概要を見る

    Stabilization and shock-capturing parameters introduced recently for the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation of compressible flows based on conservation variables are assessed in test computations with inviscid supersonic flows and different types of finite element meshes. The new shock-capturing parameters, categorized as "YZ beta Shock-Capturing" in this paper, are compared to earlier parameters derived based on the entropy variables. In addition to being much simpler, the new shock-capturing parameters yield better shock quality in the test computations, with more substantial improvements seen for triangular elements. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Preface

    Tezduyar T.E, Masud A

    International Journal for Numerical Methods in Fluids   54 ( 6-8 ) 591  2007年  [査読有り]

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  • Influence of wall elasticity in patient-specific hemodynamic simulations

    Ryo Torii, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, Tayfun E. Tezduyar

    COMPUTERS & FLUIDS   36 ( 1 ) 160 - 168  2007年01月  [査読有り]

     概要を見る

    Recent reports indicate that the rupture risk for cerebral aneurysms is less than the risk of surgical complications. Being able to predict the rupture of aneurysms would help making better-informed decisions and avoiding unnecessary surgical operations. The wall shear stress is known to play an important role in vascular diseases. We carry out computational fluid-structure interaction analyses to investigate the influence of the arterial-wall deformation on the hemodynamic factors, including the wall shear stress distribution. The results show various patterns of this influence, depending very much on the arterial geometry. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Fluid-structure interaction modeling of complex parachute designs with the space-time finite element techniques

    S. Sathe, R. Benney, R. Charles, E. Doucette, J. Miletti, M. Senga, K. Stein, T. E. Tezduyar

    COMPUTERS & FLUIDS   36 ( 1 ) 127 - 135  2007年01月  [査読有り]

     概要を見る

    In recent years we introduced a number of enhancements to the space-time techniques we developed for computer modeling of Fluid-Structure Interaction (FSI) problems. These enhancements, which include more sophisticated fluid-structure coupling and improved mesh generation, are enabling us to address more of the computational challenges involved. Our objective here is to demonstrate the robustness of these techniques in FSI modeling of parachutes involving complex designs. As a numerical example, we have selected a conceptual parachute design with geometric complexities resembling those seen in some of the advanced parachute designs proposed and tested in recent times. We describe our FSI modeling techniques and how we compute the descent and glide performance of this conceptual parachute design. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Finite element computation of turbulent flows with the discontinuity-capturing directional dissipation (DCDD)

    Franco Rispoli, Alessandro Corsini, Tayfun E. Tezduyar

    COMPUTERS & FLUIDS   36 ( 1 ) 121 - 126  2007年01月  [査読有り]

     概要を見る

    The streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) methods are among the most popular stabilized formulations in finite element computation of flow problems. The discontinuity-capturing directional dissipation (DCDD) was first introduced as a complement to the SUPG and PSPG stabilizations for the computation of incompressible flows in the presence of sharp solution gradients. The DCDD stabilization takes effect where there is a sharp gradient in the velocity field and introduces dissipation in the direction of that gradient. The length scale used in defining the DCDD stabilization is based on the solution gradient. Here we describe how the DCDD stabilization, in combination with the SUPG and PSPG stabilizations, can be applied to computation of turbulent flows. We examine the similarity between the DCDD stabilization and a purely dissipative energy cascade model. To evaluate the performance of the DCDD stabilization, we compute as test problem a plane channel flow at friction Reynolds number Re-tau = 180. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Erratum: Modelling of fluid-structure interactions with the space-time finite elements: Arterial fluid mechanics (International Journal for Numerical Methods in Fluids (10.1002/fld.1443))

    Tezduyar T.E, Sathe S, Cragin T, Nanna B, Conklin B.S, Pausewang J, Schwaab M

    International Journal for Numerical Methods in Fluids   54 ( 6-8 )  2007年  [査読有り]

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  • Editorial

    Tezduyar T.E, Matsumoto Y, Hughes T.J.R, Hafez M

    Computers and Fluids   36 ( 1 ) 1  2007年  [査読有り]

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  • Computation of flow problems with the Mixed Interface-Tracking/Interface-Capturing Technique (MITICT)

    J. Ed Akin, Tayfun E. Tezduyar, Mehmet Ungor

    COMPUTERS & FLUIDS   36 ( 1 ) 2 - 11  2007年01月  [査読有り]

     概要を見る

    In computation of flow problems with fluid-solid interfaces, an interface-tracking technique, where the fluid mesh moves to track the interface, would allow us to have full control of the resolution of the fluid mesh in the boundary layers. With an interface-capturing technique (or an interface locator technique in the more general case), on the other hand, independent of how accurately the interface geometry is represented, the resolution of the fluid mesh in the boundary layer will be limited by the resolution of the fluid mesh at the interface. In computation of flow problems with fluid-fluid interfaces where the interface is too complex or unsteady to track while keeping the remeshing frequency under control, interface-capturing techniques, with enhanced-discretization as needed, could be used as more flexible alternatives. Sometimes we may need to solve flow problems with both fluid-solid interfaces and complex or unsteady fluid-fluid interfaces. The Mixed Interface-Tracking/Interface-Capturing-Technique (MITICT) was introduced for computation of flow problems that involve both interfaces that can be accurately tracked with a moving mesh method and interfaces that are too complex or unsteady to be tracked and therefore require an interface-capturing technique. As the interface-tracking technique, We use the Defonning-Spatial-Domain/Stabilized Space Time (DSD/SST) formulation. The interface-capturing technique rides on this, and is based on solving over a moving mesh, in addition to the Navier-Stokes equations, the advection equation governing the time-evolution of the interface function. For the computations reported in this paper, as interface-capturing technique we are using one of the versions of the Edge-Tracked Interface Locator Technique (ETILT). (c) 2005 Elsevier Ltd. All rights reserved.

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  • Special issue of computational mechanics on stabilized, multiscale and multiphysics methods

    A Masud, TE Tezduyar

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 293 - 293  2006年09月  [査読有り]

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  • Improved discontinuity-capturing finite element techniques for reaction effects in turbulence computation

    A Corsini, F Rispoli, A Santoriello, TE Tezduyar

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 356 - 364  2006年09月  [査読有り]

     概要を見る

    Recent advances in turbulence modeling brought more and more sophisticated turbulence closures (e.g. k-epsilon, k-epsilon-v(2)-f, Second Moment Closures), where the governing equations for the model parameters involve advection, diffusion and reaction terms. Numerical instabilities can be generated by the dominant advection or reaction terms. Classical stabilized formulations such as the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation (Brook and Hughes, comput methods Appl Mech Eng 32:199-255, 1982; Hughes and Tezduyar, comput methods Appl Mech Eng 45: 217-284, 1984) are very well suited for preventing the numerical instabilities generated by the dominant advection terms. A different stabilization however is needed for instabilities due to the dominant reaction terms. An additional stabilization term, called the diffusion for reaction-dominated (DRD) term, was introduced by Tezduyar and Park (comput methods Appl Mech Eng 59:307-325, 1986) for that purpose and improves the SUPG performance. In recent years a new class of variational multi-scale (VMS) stabilization (Hughes, comput methods Appl Mech Eng 127:387-401, 1995) has been introduced, and this approach, in principle, can deal with advection-diffusion-reaction equations. However, it was pointed out in Hanke (comput methods Appl Mech Eng 191:2925-2947) that this class of methods also need some improvement in the presence of high reaction rates. In this work we show the benefits of using the DRD operator to enhance the core stabilization techniques such as the SUPG and VMS formulations. We also propose a new operator called the DRDJ (DRD with the local variation jump) term, targeting the reduction of numerical oscillations in the presence of both high reaction rates and sharp solution gradients. The methods are evaluated in the context of two stabilized methods: the classical SUPG formulation and a recently-developed VMS formulation called the V-SGS (Corsini et al. comput methods Appl Mech Eng 194:4797-4823, 2005). Model problems and industrial test cases are computed to show the potential of the proposed methods in simulation of turbulent flows.

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  • Fluid-structure interaction modeling of aneurysmal conditions with high and normal blood pressures

    R Torii, M Oshima, T Kobayashi, K Takagi, TE Tezduyar

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 482 - 490  2006年09月  [査読有り]

     概要を見る

    Hemodynamic factors like the wall shear stress play an important role in cardiovascular diseases. To investigate the influence of hemodynamic factors in blood vessels, the authors have developed a numerical fluid-structure interaction (FSI) analysis technique. The objective is to use numerical simulation as an effective tool to predict phenomena in a living human body. We applied the technique to a patient-specific arterial model, and with that we showed the effect of wall deformation on the WSS distribution. In this paper, we compute the interaction between the blood flow and the arterial wall for a patient-specific cerebral aneurysm with various hemodynamic conditions, such as hypertension. We particularly focus on the effects of hypertensive blood pressure on the interaction and the WSS, because hypertension is reported to be a risk factor in rupture of aneurysms. We also aim to show the possibility of FSI computations with hemodynamic conditions representing those risk factors in cardiovascular disease. The simulations show that the transient behavior of the interaction under hypertensive blood pressure is significantly different from the interaction under normal blood pressure. The transient behavior of the blood-flow velocity, and the resulting WSS and the mechanical stress in the aneurysmal wall, are significantly affected by hypertension. The results imply that hypertension affects the growth of an aneurysm and the damage in arterial tissues.

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  • Enhanced-discretization selective stabilization procedure (EDSSP)

    TE Tezduyar, S Sathe

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 456 - 468  2006年09月  [査読有り]

     概要を見る

    The enhanced-discretization selective stabilization procedure (EDSSP) provides a multiscale framework for applying numerical stabilization selectively at different scales. The EDSSP is based on the enhanced-discretization, multiscale function space concept underlying the enhanced- discretization successive update method (EDSUM). The EDSUM is a multi-level iteration method designed for computation of the flow behavior at small scales. It has a built-in mechanism for transferring flow information between the large and small scales in a fashion consistent with the discretizations resulting from the underlying stabilized formulations. This is accomplished without assuming that the small-scale trial or test functions vanish at the borders between the neighboring large-scale elements of the enhanced-discretization zones. This facilitates unrestricted movement of small-scale flow patterns from one large-scale element to another without any constraints at the border between the two elements. The enhanced-discretization concept underlying the EDSUM can also facilitate using different stabilizations for equations or unknowns corresponding to different scales. In this paper we propose a version of the EDSSP where the SUPG and PSPG stabilizations are used for unknowns corresponding to both the large and small scales but the discontinuity-capturing stabilizations are used for unknowns corresponding to only the small scales. We also propose a version where a linear discontinuity-capturing is used for the small-scale unknowns and a nonlinear discontinuity-capturing is used for the large-scale unknowns. We evaluate the performances of these versions of the EDSSP with test problems governed by the advection-diffusion equations.

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  • Computation of inviscid supersonic flows around cylinders and spheres with the SUPG formulation and Y Z beta shock-capturing

    TE Tezduyar, M Senga, D Vicker

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 469 - 481  2006年09月  [査読有り]

     概要を見る

    Numerical experiments with inviscid supersonic flows around cylinders and spheres are carried out to evaluate the stabilization and shock-capturing parameters introduced recently for the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation of compressible flows based on conservation variables. The tests with the cylinders are carried out for both structured and unstructured meshes. The new shock-capturing parameters, which we call "YZ beta Shock-Capturing", are compared to earlier SUPG parameters derived based on the entropy variables. In addition to being much simpler, the new shock-capturing parameters yield better shock quality in the test computations, with more substantial improvements seen for unstructured meshes with triangular and tetrahedral elements. Furthermore, the results obtained with YZ beta Shock-Capturing compare very favorably to those obtained with the well established OVERFLOW code.

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  • Compressible flow SUPG stabilization parameters computed from degree-of-freedom submatrices

    L Catabriga, ALGA Coutinho, TE Tezduyar

    COMPUTATIONAL MECHANICS   38 ( 4-5 ) 334 - 343  2006年09月  [査読有り]

     概要を見る

    We present, for the SUPG formulation of inviscid compressible flows, stabilization parameters defined based on the degree-of-freedom submatrices of the element-level matrices. With 2D steady-state test problems involving supersonic flows and shocks, we compare these stabilization parameters with the ones defined based on the full element-level matrices. We also compare them to the stabilization parameters introduced in the earlier development stages of the SUPG formulation of compressible flows. In all cases the formulation includes a shock-capturing term involving a shock-capturing parameter. We investigate the difference between updating the stabilization and shock-capturing parameters at the end of every time step and at the end of every nonlinear iteration within a time step. The formulation includes, as an option, an algorithmic feature that is based on freezing the shock-capturing parameter at its current value when a convergence stagnation is detected.

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  • Stabilization and shock-capturing parameters in SUPG formulation of compressible flows

    TE Tezduyar, M Senga

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 13-16 ) 1621 - 1632  2006年  [査読有り]

     概要を見る

    The streamline-upwind/Petrov-Galerkin (SUPG) formulation is one of the most widely used stabilized methods in finite element computation of compressible flows. It includes a stabilization parameter that is known as "tau". Typically the SUPG formulation is used in combination with a shock-capturing term that provides additional stability near the shock fronts. The definition of the shock-capturing term includes a shock-capturing parameter. In this paper, we describe, for the finite element formulation of compressible flows based on conservation variables, new ways for determining the T and the shock-capturing parameter. The new definitions for the shock-capturing parameter are much simpler than the one based on the entropy variables, involve less operations in calculating the shock-capturing term, and yield better shock quality in the test computations. (c) 2005 Elsevier B.V. All rights reserved.

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  • Space-time finite element techniques for computation of fluid-structure interactions

    TE Tezduyar, S Sathe, R Keedy, K Stein

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 17-18 ) 2002 - 2027  2006年  [査読有り]

     概要を見る

    We describe the space-time finite element techniques we developed for computation of fluid-structure interaction (FSI) problems. Among these techniques are the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation and its special version, and the mesh update methods, including the solid-extension mesh moving technique (SEMMT). Also among these techniques are the block-iterative, quasi-direct and direct coupling methods for the solution of the fully discretized, coupled fluid and structural mechanics equations. We present some test computations for the mesh moving techniques described. We also present numerical examples where the fluid is governed by the Navier-Stokes equations of incompressible flows and the structure is governed by the membrane and cable equations. Overall, we demonstrate that the techniques we have developed have increased the scope and accuracy of the methods used in computation of FSI problems. (c) 2005 Elsevier B.V. All rights reserved.

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  • Solution techniques for the fully discretized equations in computation of fluid-structure interactions with the space-time formulations

    Tayfun E. Tezduyar, Sunil Sathe, Keith Stein

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 41-43 ) 5743 - 5753  2006年  [査読有り]

     概要を見る

    We provide an overview of the solution techniques we have developed for the fully discretized equations encountered at every time step in computation of fluid-structure interactions with the space-time techniques. These coupled, nonlinear equations are generated from the finite element discretization of the governing equations for the fluid mechanics, structural mechanics and the motion of the fluid mechanics mesh. The fluid mechanics equations are discretized with the deforming-spatial-domain/stabilized space time formulation. The mesh motion is governed by the equations of elasticity, with the smaller elements stiffened in the finite element formulation. The coupled, fully discretized equations are solved with the block-iterative, quasi-direct and direct coupling methods. We present numerical examples with incompressible flows and membrane and cable structures. (c) 2005 Elsevier B.V. All rights reserved.

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  • Parallel finite element computations in fluid mechanics

    TE Tezduyar, A Sameh

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 13-16 ) 1872 - 1884  2006年  [査読有り]

     概要を見る

    We provide an overview of the role of parallel finite element computations in fluid mechanics. We emphasize the class of flow problems involving moving boundaries and interfaces. Some of the computationally most challenging flow problems, such as fluid-object and fluid-structure interactions as well as free-surface and two-fluid flows, belong to this class. In the development of the methods targeting this class of problems, the computational challenges involved need to be addressed in such a way that 3D computation of complex applications can be carried out efficiently on parallel computers. This requirement has to be one of the key factors in designing various components of the overall solution approach, such as solution techniques for the discretized equations and mesh update methods for handling the changes in the spatial domain occupied by the fluid. This overview includes a description of how the computational challenges are addressed and how the computational schemes can be enhanced with special preconditioning techniques. (c) 2005 Elsevier B.V. All rights reserved.

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  • Modeling of fluid-structure interactions with the space-time techniques

    Tezduyar T.E, Sathe S, Stein K, Aureli L

    Lecture Notes in Computational Science and Engineering   53   50 - 81  2006年  [査読有り]

  • Interface-tracking and interface-capturing techniques for finite element computation of moving boundaries and interfaces

    TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 23-24 ) 2983 - 3000  2006年  [査読有り]

     概要を見る

    We provide an overview of some of the interface-tracking and interface-capturing techniques we developed for finite element computation of flow problems with moving boundaries and interfaces. This category of flow problems includes fluid-particle, fluid-object and fluid-structure interactions; free-surface and two-fluid flows; and flows with moving mechanical components. Both classes of techniques are based on stabilized formulations. The interface-tracking techniques are based on the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation, where the mesh moves to track the interface. The interface-capturing techniques, developed primarily for free-surface and two-fluid interface flows. are formulated typically over non-moving meshes, using an advection equation in addition to the flow equations. The advection equation governs the evolution of an interface function that marks the location of the interface. We also highlight some of the methods we developed to increase the scope and accuracy of these two classes of techniques. (c) 2005 Elsevier B.V. All rights reserved.

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  • Computer modeling of cardiovascular fluid-structure interactions with the deforming-spatial-domain/stabilized space-time formulation

    R Torii, M Oshima, T Kobayashi, K Takagi, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 13-16 ) 1885 - 1895  2006年  [査読有り]

     概要を見る

    Hemodynamic factors such as the wall shear stress are believed to affect a number of cardiovascular diseases including atherosclerosis and aneurysm. Since resolving phenomena in a living human body is currently beyond the capabilities of in vivo measurement techniques, computer modeling is expected to play an important role in gaining a better understanding of the relationship between the cardiovascular diseases and the hemodynamic factors. We have developed a computer modeling technique for cardiovascular hemodynamic simulations. With this modeling technique, patient-specific 3D geometry of an artery can be analyzed. We take into account some of the important factors in human body for the purpose of demonstrating in vivo situations in a virtual world. The interaction between the blood flow and the deformation of the arterial walls is a factor that we are specifically focusing on. For such fluid-structure interactions, we have developed a computer modeling tool based oil the deforming-spatial-domain/stabilized spacetime (DSD/SST) formulation. This simulation tool is applied to a patient-specific model under pulsatile blood flow conditions. The Simulations show that the flow behavior with compliant arterial walls is different from what we see with rigid arterial walls. Consequently, the distribution of the wall shear stress on the compliant arterial walls is significantly different from that on the rigid arterial walls. We deduce that the compliance of the arterial walls needs to be taken into account in cardiovascular hemodynamic simulations, and the computer modeling tool we have developed can be effective in investigation of cardiovascular diseases. (c) 2005 Elsevier B.V. All rights reserved.

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  • A tribute to Thomas J.R Hughes on the occasion of his 60th birthday

    A Masud, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 13-16 ) 1281 - 1282  2006年  [査読有り]

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  • A robust preconditioner for fluid-structure interaction problems (vol 194, pg 4027, 2005)

    T Washio, T Hisada, H Watanabe, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   195 ( 19-22 ) 2861 - 2861  2006年  [査読有り]

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  • Compressible flow SUPG parameters computed from element matrices

    L Catabriga, ALGA Coutinho, TE Tezduyar

    COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING   21 ( 9 ) 465 - 476  2005年09月  [査読有り]

     概要を見る

    We present, for the SUPG formulation of inviscid compressible flows with shocks, stabilization parameters defined based on the element-level matrices. These definitions are expressed in terms of the ratios of the norms of the matrices and take into account the flow field, the local length scales, and the time step size. Calculations of these stabilization parameters are straightforward and do not require explicit expressions for length or velocity scales. We compare the performance of these stabilization parameters, accompanied by a shock-capturing parameter introduced earlier, with the performance of a stabilization parameter introduced earlier, accompanied by the same shock-capturing parameter. We investigate the performance difference between updating the stabilization and shock-capturing parameters at the end of every time step and at the end of every non-linear iteration within a time step. We also investigate the influence of activating an algorithmic option that was introduced earlier, which is based on freezing the shock-capturing parameter at its current value when a convergence stagnation is detected. Copyright (C) 2005 John Wiley & Sons, Ltd.

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  • Moving-interface computations with the edge-tracked interface locator technique (ETILT)

    MA Cruchaga, DJ Celentano, TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   47 ( 6-7 ) 451 - 469  2005年02月  [査読有り]

     概要を見る

    We describe, for simulation of flows with moving interfaces, a computational method based on the edge-tracked interface locator technique (ETILT). The method described has been designed by bearing in mind the ease in managing a node-based interface representation and the interface sharpness and volume conservation features of the Moving Lagrangian Interface Technique. We evaluate the performance of the method with a number of test problems: filling of a step cavity, gravity-driven flow of an aluminium alloy in an obstructed channel, collapse of a liquid column, and the bore problem. Copyright (C) 2004 John Wiley Sons, Ltd.

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  • Fluid-structure interaction modelling of parachute soft-landing dynamics

    K Stein, TE Tezduyar, S Sathe, R Benney, R Charles

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   47 ( 6-7 ) 619 - 631  2005年02月  [査読有り]

     概要を見る

    Soft landing of a payload with the aid of a retraction device is an important aspect in cargo parachute operations. Accurate simulation of this class of parachute operations with a computer model that takes into account the fluid-structure interactions involved would complement drop tests and support the design of cargo parachute systems. We describe the computational methods developed for this purpose, demonstrate how the computational model works in investigation of different soft-landing conditions, and show a good correlation between the data from our simulations and drop tests. Copyright (C) 2004 John Wiley Sons, Ltd.

    DOI

  • Enhanced-discretization successive update method (EDSUM)

    TE Tezduyar, S Sathe

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   47 ( 6-7 ) 633 - 654  2005年02月  [査読有り]

     概要を見る

    The enhanced-discretization successive update method (EDSUM) is a multi-level iteration method designed for computation of the flow behaviour at small scales. As an enhancement in iterative solution of non-linear and linear equation systems, the EDSUM is one of the enhanced discretization and solution techniques developed for more effective Computation of complex flow problems. It complements techniques based on enhancement in spatial discretization and based on enhancement in time discretization in the context of a space-time formulation. It is closely related to the enhanced-discretization interface-capturing technique (EDICT), as the function spaces used in the EDSUM are very similar to those used in the EDICT. The EDSUM also has a built-in mechanism for transferring flow information between the large and small scales in a fashion consistent with the discretizations resulting from the underlying stabilized formulations. With a number of test computations for steady-state problems governed by the advection-diffusion equation, we demonstrate that the EDSUM has the potential to become a competitive technique for computation of flow behaviour at small scales. Copyright (C) 2004 John Wiley Sons, Ltd.

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  • Space-time finite element techniques for computation of fluid-structure interactions

    Tezduyar T.E, Sathe S, Keedy R, Stein K

    11th International Conference on Fracture 2005, ICF11   2   1315 - 1317  2005年  [査読有り]

  • Preface

    Tezduyar T.E, Hafez M

    International Journal for Numerical Methods in Fluids   47 ( 6-7 ) 449  2005年  [査読有り]

    DOI

  • Overview of the airdrop systems modeling project within the Collaborative Simulation and Test (CST) Common High Performance Computing Software Support Initiative (CHSSI) portfolio

    Charles R, Accorsi M, Morton S, Tomaro R, Stein K, Sathe S, Tezduyar T

    Collection of Technical Papers - 18th AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar     203 - 211  2005年  [査読有り]

  • A robust preconditioner for fluid-structure interaction problems

    T Washio, T Hisada, H Watanabe, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   194 ( 39-41 ) 4027 - 4047  2005年  [査読有り]

     概要を見る

    Two preconditioners are presented for equation systems of strongly coupled fluid-structure interaction computations where the structure is modeled by shell elements. These preconditioners fall into the general category of incomplete LU factorization. The two differ mainly in whether the coefficient matrix is factorized node by node or variable-by-variable. In the variable-wise preconditioner, a modified Schur complement system for pressure is solved approximately with a few iterations using a special preconditioner. The efficiencies of the two preconditioners are compared for different finite element formulations of the fluid mechanics part, including formulations with SUPG and PSPG stabilizations. (c) 2004 Elsevier B.V. All rights reserved.

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  • Special issue: Flow simulation and modeling - Preface

    TE Tezduyar, TJR Hughes

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   193 ( 21-22 ) III - III  2004年  [査読有り]

    DOI

  • SUPG stabilization parameters calculated from the quadrature-point components of the element-level matrices

    Akin J.E, Tezduyar T.E

    ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering    2004年  [査読有り]

  • Numerical simulation of soft landing for clusters of cargo parachutes

    Stein K.R, Tezduyar T.E, Kumar V, Sathe S.V, Benney R.J, Charles R.D

    ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering    2004年  [査読有り]

  • Methods for computation of moving boundaries and interfaces

    Tezduyar T.E

    ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering    2004年  [査読有り]

  • Influence of wall elasticity on image-based blood flow simulations

    Torii R, Oshima M, Kobayashi T, Takagi K, Tezduyar T.E

    Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A   70 ( 9 ) 1224 - 1231  2004年  [査読有り]

    DOI

  • Enhanced-discretization space-time technique (EDSTT)

    TE Tezduyar, S Sathe

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   193 ( 15-16 ) 1385 - 1401  2004年  [査読有り]

     概要を見る

    The enhanced-discretization space-time technique (EDSTT) was developed for the purpose of being able to, in the context of a space-time formulation, enhance the time-discretization in regions of the fluid domain requiring smaller time steps. Such requirements are often encountered in time-accurate computations of fluid-structure interactions, where the time-step size required by the structural dynamics part is smaller, and carrying out the entire computation with that time-step size would be too inefficient for the fluid dynamics part. In the EDSTT-single-mesh (EDSTT-SM) approach, a single space-time mesh. unstructured both in space and time, would be used to enhance the time-discretization in regions requiring smaller time steps. In the EDSTT-multi-mesh (EDSTT-MM) approach, we complement the space-time concept of the deforming-spatial-domain/stabilized space-time (DSD/SST) formulation with the multimesh concept of the enhanced-discretization interface-capturing technique (EDICT). In applications to fluid-structure interactions, the structural dynamics modeling is based oil a single space-time mesh and the fluid dynamics modeling is based on two space-time meshes. The structural dynamics interface nodes in the space-time domain also belong to the second fluid mesh, which accommodates the time-step requirement of the Structural dynamics. We apply the EDSTT-SM and EDSTT-MM approaches to a number of test problems to demonstrate how these methods work and why they would be desirable to use in time-accurate computations. (C) 2004 Elsevier B.V. All rights reserved.

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  • Enhanced-approximation linear solution technique (EALST)

    TE Tezduyar, S Sathe

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   193 ( 21-22 ) 2033 - 2049  2004年  [査読有り]

     概要を見る

    The enhanced discretization and solution techniques are among the advanced computational methods we rely on in simulation and modeling of complex flow problems, including those with moving boundaries and interfaces. The set of enhanced discretization and solution techniques includes those based on enhancement in spatial discretization, enhancement in time discretization, and enhancement in iterative solution of nonlinear and linear equation systems. The enhanced-approximation linear solution technique (EALST) was introduced to increase the performance of the iterative technique used in solution of the linear equation systems when some parts of the computational domain may offer more of a challenge for the iterative method than the others. The EALST can be used for computations based on serni-discrete or space-time formulations. (C) 2004 Elsevier B.V. All rights reserved.

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  • Discontinuity-capturing directional dissipation (DCDD) in computation of turbulent flows

    Rispoli F, Borrelli P, Tezduyar T.E

    ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering    2004年  [査読有り]

  • Determination of the stabilization and shock-capturing parameters in supg formulation of compressible flows

    Tezduyar T.E

    ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering    2004年  [査読有り]

  • Calculation of the advective limit of the SUPG stabilization parameter for linear and higher-order elements

    JE Akin, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   193 ( 21-22 ) 1909 - 1922  2004年  [査読有り]

     概要を見る

    We investigate.. for linear and higher-order elements, various ways of calculating the advective limit of the stabilization parameter ("tau") used in the streamline-upwind/Petrov-Galerkin (SUPG) formulation of flow problems. In the context of a pure advection test problem, we compare the "UGN-based", element-matrix-based, and element-node-based calculations of the advective limit of the tau. Our investigation shows that the performances of the "UGN-based" and element-matrix -based tau definitions are comparable, with the element-matrix-based definition yielding somewhat lower tau values. We also show that for both definitions, as the polynomial orders increase, the tau values decrease, as they should. (C) 2004 Elsevier B.V. All rights reserved.

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  • Automatic mesh update with the solid-extension mesh moving technique

    K Stein, TE Tezduyar, R Benney

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   193 ( 21-22 ) 2019 - 2032  2004年  [査読有り]

     概要を見る

    In computation of fluid-structure interactions involving large displacements, we use a mesh update method composed of mesh moving and remeshing-as-needed. For problems with complex geometries, we need automatic mesh moving techniques that reduce the need for remeshing. We also would like that these mesh moving techniques allow us to control mesh resolution near the fluid-structure interfaces so that we can represent the boundary layers more accurately. In the mesh moving techniques we designed, the motion of the nodes is governed by the equations of elasticity, and mesh deformation is handled selectively based on element sizes and deformation modes. This is helping us reduce the frequency of remeshing. With the solid-extension mesh moving technique presented in this paper, we are also able to limit mesh distortion in thin layers of elements placed near fluid-structure interfaces. (C) 2004 Elsevier B.V. All rights reserved.

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  • Computation of moving boundaries and interfaces and stabilization parameters

    TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   43 ( 5 ) 555 - 575  2003年10月  [査読有り]

     概要を見る

    The interface-tracking and interface-capturing techniques we developed in recent years for computation of flow problems with moving boundaries and interfaces rely on stabilized formulations such as the streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) methods. The interface-tracking techniques are based on the deforming-spatial-domain/stabilized space-time formulation, where the mesh moves to track the interface. The interface-capturing techniques, typically used with non-moving meshes, are based on a stabilized semi-discrete formulation of the Navier-Stokes equations, combined with a stabilized formulation of the advection equation governing the time-evolution of an interface function marking the interface location. We provide an overview of the interface-tracking and interface-capturing techniques, and highlight how we determine the stabilization parameters used in the stabilized formulations. Copyright (C) 2003 John Wiley Sons, Ltd.

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  • Stabilization parameters and smagorinsky turbulence model

    JE Akin, T Tezduyar, M Ungor, S Mittal

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   70 ( 1 ) 2 - 9  2003年01月  [査読有り]

     概要を見る

    For the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin formulations for flow problems, we present in this paper a comparative study of the stabilization parameters defined in different ways. The stabilization parameters are closely related to the local lenght scales ("element lenght") and our comparisons include parameters defined based on the element-level matrices and vectors, some earlier definitions of element lengths, and extensions of these to higher-order elements. We also compare the numerical viscosities generated by these stabilized formulations with the eddy viscosity associated with a Smagorinsky turbulence model that is based on element length scales.

    DOI

  • Simulation of parachute dynamics during control line input operations

    Stein K, Tezduyar T, Sathe S, Senga M, Ozcan C, Soltys T, Kumar V, Benney R, Charles R

    17th AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar    2003年  [査読有り]

  • Mesh moving techniques for fluid-structure interactions with large displacements

    K Stein, T Tezduyar, R Benney

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   70 ( 1 ) 58 - 63  2003年01月  [査読有り]

     概要を見る

    In computation of fluid-structure interactions, we use mesh update methods consisting of mesh-moving and remeshing-as-needed. When the geometries are complex and the structural displacements are large, it becomes even more important that the mesh moving techniques are designed with the objective to reduce the frequency of remeshing. To that end, we present here mesh moving techniques where the motion of the nodes is governed by the equations of elasticity, with selective treatment of mesh deformation based on element sizes as well as deformation modes in terms of shape and volume changes. We also present results from application of these techniques to a set of two-dimensional test cases.

    DOI

  • Journal of Applied Mechanics, Transactions ASME: Preface

    Tezduyar T.E, Hughes T.J.R

    Journal of Applied Mechanics, Transactions ASME   70 ( 1 ) 1  2003年  [査読有り]

    DOI

  • Computational methods for modeling parachute systems

    K Stein, T Tezduyar, R Benney

    COMPUTING IN SCIENCE & ENGINEERING   5 ( 1 ) 39 - 46  2003年01月  [査読有り]

     概要を見る

    Using computational models in parachute system development can improve performance. For successful modeling, however, several challenges must be addressed, particularly the interaction between the parachute structural dynamics and the aerodynamics.

    DOI

  • Airdrop simulations of controlled parachute descentst

    R Charles, R Benney, K Stein, T Tezduyar, S Sathe, M Senga, C Ozcan, T Soltys, Kumar, V, M Accorsi, Z Xu, B Zhou

    2003 USERS GROUP CONFERENCE, PROCEEDINGS     160 - 164  2003年  [査読有り]

     概要を見る

    Computational simulation tools have been applied to a variety of applications relating to the control of parachute descent. The simulation tools have three components: the computation of the structural dynamics (CSD); the computation of the fluid dynamics of the air stream (CFD); and the mutual interface between two that make up the fluid-structure interactions (FSI). In the area of CSD, element contact methodologies have been investigated and tested. FSI developments have focused on the application of line input controls and soft-landing techniques for round canopies. In addition, long duration simulation results have been performed and compared qualitatively with the results from experimental investigations.

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  • Aerodynamic interactions between parachute canopies

    K Stein, T Tezduyar, Kumar, V, S Sathe, R Benney, E Thornburg, C Kyle, T Nonoshita

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   70 ( 1 ) 50 - 57  2003年01月  [査読有り]

     概要を見る

    Aerodynamic interactions between parachute canopies can occur when two separate parachutes come close to each other or in a cluster of parachutes. For the case of two separate parachutes, our computational study focuses on the effect of the separation distance on the aerodynamic interactions, and also focuses on the fluid-structure interactions with given initial relative positions. For the aerodynamic interactions between the canopies of a cluster of parachutes, we focus on the effect of varying the number and arrangement of the canopies.

    DOI

  • Computation of mould filling processes with a moving Lagrangian interface technique

    M Cruchaga, D Celentano, T Tezduyar

    COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING   18 ( 7 ) 483 - 493  2002年07月  [査読有り]

     概要を見る

    Computation of non-isothermal flow problems involving moving interfaces is presented. A Lagrangian interface technique, defined in the context of a fixed-mesh finite element formulation for incompressible flows, is employed to update the interface position. A global mass-corrector algorithm is used to accurately enforce the global mass conservation. The Navier-Stokes equations are solved with an improved sub-element integration technique to more accurately account for sudden changes in the fluid properties across the interface. The method described is applied to two mould filling problems. Copyright (C) 2002 John Wiley Sons, Ltd.

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  • Impulsively started flow about a rigid parachute canopy

    H Johari, K Stein, T Tezduyar

    JOURNAL OF AIRCRAFT   38 ( 6 ) 1102 - 1109  2001年11月  [査読有り]

     概要を見る

    The temporal evolution of the flowfield in the near wake of a parachute canopy is studied computationally with a finite element method. The canopy is assumed to be rigid and impermeable, and the flow is started impulsively. The separated shear layer surrounding the canopy creates a starting vortex ring. As time evolves, flow instabilities cause the vortex ring to become convoluted and eventually lead to the breakup of the ring. This phase of the flow lasts for approximately 16D/U, where D is the mean projected diameter of the canopy and U is the freestream velocity. After the initial phase, the flow goes through a transition phase before settling into its steady state. In the steady-state phase, the drag and base pressure coefficient become nearly constant. The computed drag coefficient matches very well against experimental data. The steady-state phase is reached after a time period of approximately 45D/U. During the steady-state phase, vortex shedding is observed in the near wake despite the nearly constant drag coefficient.

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  • Fluid-structure interactions of a round parachute: Modeling and simulation techniques

    KR Stein, RJ Benney, TE Tezduyar, JW Leonard, ML Accorsi

    JOURNAL OF AIRCRAFT   38 ( 5 ) 800 - 808  2001年09月  [査読有り]

     概要を見る

    A parallel computational technique is presented for carrying out three-dimensional simulations of parachute fluid-structure interactions, and this technique is applied to simulations of airdrop performance and control phenomena in terminal descent. The technique uses a stabilized space-time formulation of the time-dependent, three-dimensional Navier-Stokes equations of incompressible flows for the fluid dynamics part. Turbulent features of the flow are accounted for by using a zero-equation turbulence model. A finite element formulation derived from the principle of virtual work is used for the parachute structural dynamics. The parachute is represented as a cable-membrane tension structure. Coupling of the fluid dynamics with the structural dynamics is implemented over the fluid-structure interface, which is the parachute canopy surface. Large deformations of the structure require that the fluid dynamics mesh is updated at every time step, and this is accomplished with an automatic mesh-moving method. The parachute used in the application presented here is a standard U.S. Army personnel parachute.

    DOI

  • Fluid-structure interactions of a round parachute: Modeling and simulation techniques

    KR Stein, RJ Benney, TE Tezduyar, JW Leonard, ML Accorsi

    JOURNAL OF AIRCRAFT   38 ( 5 ) 800 - 808  2001年09月  [査読有り]

     概要を見る

    A parallel computational technique is presented for carrying out three-dimensional simulations of parachute fluid-structure interactions, and this technique is applied to simulations of airdrop performance and control phenomena in terminal descent. The technique uses a stabilized space-time formulation of the time-dependent, three-dimensional Navier-Stokes equations of incompressible flows for the fluid dynamics part. Turbulent features of the flow are accounted for by using a zero-equation turbulence model. A finite element formulation derived from the principle of virtual work is used for the parachute structural dynamics. The parachute is represented as a cable-membrane tension structure. Coupling of the fluid dynamics with the structural dynamics is implemented over the fluid-structure interface, which is the parachute canopy surface. Large deformations of the structure require that the fluid dynamics mesh is updated at every time step, and this is accomplished with an automatic mesh-moving method. The parachute used in the application presented here is a standard U.S. Army personnel parachute.

  • The multi-domain method for computation of the aerodynamics of a parachute crossing the far wake of an aircraft

    T Tezduyar, Y Osawa

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   191 ( 6-7 ) 705 - 716  2001年  [査読有り]

     概要を見る

    We present the multi-domain method (MDM) for computation of unsteady flow past a cargo aircraft and around a parachute crossing the aircraft's far wake. The base computational methods used here are the stabilized semi-discrete and space-time finite element formulations developed earlier. In the MDM, the computational domain is divided into an ordered sequence of overlapping subdomains. The flow field computed over Subdomain-1, which contains the aircraft, supplies the inflow boundary conditions for Subdomain-2, which is used for computing the long-wake flow. Subdomain-3 contains the parachute, and moves across Subdomain-2. The boundary conditions for Subdomain-3 are extracted from the flow field computed over Subdomain-2, at locations corresponding to the positions of the boundaries of Subdomain-3 as it crosses Subdomain-2. The computation over Subdomain-1, which contains a complex but fixed object, is based on a general-purpose implementation of the semi-discrete formulation. The computation over Subdomain-2, which contains no objects, is based on a special-purpose implementation that exploits the simplicity of the mesh to increase the computational speed. The computation over Subdomain-3, which contains a complex and moving object, is based on a general-purpose implementation of the space-time formulation. With a numerical example, we show that different methods Call be brought together in the context of the MDM to address the computational challenges involved in the aerodynamics of a parachute crossing the far wake of an aircraft. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Special issue: Minisymposium on methods for flow simulation and modeling - Preface

    TE Tezduyar, TJR Hughes

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   191 ( 6-7 ) 513 - 513  2001年  [査読有り]

    DOI

  • Shear-slip mesh update in 3D computation of complex flow problems with rotating mechanical components

    M Behr, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 24-25 ) 3189 - 3200  2001年  [査読有り]

     概要を見る

    In this paper we present a 3D computational technique fur simulation of complex, real-world flow problems with fast-rotating mechanical components. This technique is based on the Deformable-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, Shear-Slip Mesh Update Method (SSMUM), and an efficient parallel implementation for distributed-memory parallel computing platforms. The DSD/SST formulation was developed earlier for flow problems with moving boundaries and interfaces. including flows with moving mechanical components. The DSD/SST formulation requires. as a companion method. an effective mesh update strategy. especially in complex Row problems. The SSMUM was developed to meet the mesh update requirements in simulation of flow problems with fast translations, and recently, with a new version of SSMUM. fast rotations. As an example of the class of challenging simulations that can be carried out by this technique. we present computation of Row around a helicopter with its rotor in motion. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Methods for 3D computation of fluid-object interactions in spatially periodic flows

    A Johnson, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 24-25 ) 3201 - 3221  2001年  [査読有り]

     概要を見る

    We present computational methods for 3D simulation of fluid-object interactions in spatially periodic Rows. These methods include a stabilized space-time finite element formulation for incompressible Rows with spatial periodicity, automatic mesh generation and update techniques for fluid-object mixtures with spatial periodicity. and parallel implementations. The methods can be applied to uni-periodic (i.e., periodic in one direction). bi-periodic. or tri-periodic Rows. The methods are described here in the context of tri-periodic Rows with fluid-object interactions, and are applied to the simulation of sedimentation of particles in a fluid. We present several case studies where the results obtained provide notable insight into the behavior of fluid particle mixtures during sedimentation. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Fluid-structure interactions of a parachute crossing the far wake of an aircraft

    T Tezduyar, Y Osawa

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   191 ( 6-7 ) 717 - 726  2001年  [査読有り]

     概要を見る

    In this paper we describe a computational technique for simulation of the fluid-structure interactions of a parachute crossing the far wake of an aircraft. This technique relies on using the long-wake flow data already computed, in our case, with the Multi-Domain Method (MDM) we developed earlier. The fluid-structure interaction computations are carried out over a domain enclosing the parachute and moving with the payload. This domain functions as one of the subdomains of the MDM designed specifically for the parachute fluid-structure interactions considered here. The boundary conditions for this subdomain are extracted from the long-wake flow data, at locations corresponding to the positions of those boundaries in the subdomain over which the wake flow data were computed. The Navier-Stokes equations of incompressible flows, governing the fluid dynamics, are solved with the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, which can handle changes in the spatial domain occupied by the fluid. This formulation is coupled to the finite element formulation used for solving the membrane equations governing the structural mechanics of the parachute canopy and the equations governing the mechanics of the suspension lines. The numerical example included demonstrates how the technique described here, functioning as a component of the MDM, enables us to simulate the fluid-structure interactions of a parachute crossing an aircraft wake. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Fluid-structure interactions of a cross parachute: numerical simulation

    K Stein, R Benney, T Tezduyar, J Potvin

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   191 ( 6-7 ) 673 - 687  2001年  [査読有り]

     概要を見る

    The dynamics of parachutes involves complex interaction between the parachute structure and the surrounding flow field. Accurate representation of parachute systems requires treatment of the problem as a fluid-structure interaction (FSI). In this paper we present the numerical simulations we performed for the purpose of comparison to a series of cross-parachute wind tunnel experiments. The FSI model consists of a 3-D fluid dynamics (FD) solver based on the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) procedure, a structural dynamics (SD) solver, and a method of coupling the two solvers. These FSI simulations include the prediction of the coupled FD and SD behavior, drag histories, flow fields, structural behavior, and equilibrium geometries for the structure. Comparisons between the numerical results and the wind tunnel data are conducted for three cross-parachute models and at three different wind tunnel flow speeds. (C) 2001 Published by Elsevier Science B.V.

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  • Finite element interface-tracking and interface-capturing techniques for flows with moving boundaries and interfaces

    Tezduyar T

    American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD   369 ( 3 ) 105 - 114  2001年  [査読有り]

  • Finite element methods for flow problems with moving boundaries and interfaces

    TE Tezduyar

    ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING   8 ( 2 ) 83 - 130  2001年  [査読有り]

     概要を見る

    This paper is an overview of the finite element methods developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM) [http://www.mems.rice.edu/TAFSM/] for computation flow problems with moving boundaries and interfaces. This class of problems include those with free surfaces, two-fluid interfaces, fluid-object and fluid-structure interactions, and moving mechanical components. The methods developed can be classified into two main categories. The interface tracking methods are based on the Deforming-Spatial-Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation, where the mesh moves to track the interface, with special attention paid to reducing the frequency of remeshing. The interface-capturing methods, typically used for free-surface and two-fluid flows, are based on the stabilized formulation, over non-moving meshes, of both the flow equations and the advection equation governing the time-evolution of an interface function marking the location of the interface. In this category, when it becomes necessary to increase the accuracy in representing the interface beyond the accuracy provided by the existing mesh resolution around the interface,he Enhanced-Discretization Interface-Capturing: Technique (EDICT) can be used to to accomplish that Real. In development of these two classes of methods, we had to keep in mind the requirement that tilt methods need to be applicable to 3D problems with complex geometries and that the associated large-scale computations need to be carried out on parallel computing platforms. Therefore our parallel implementations of these methods are based on unstructured grids and on both the distributed and shared memory parallel computing approaches. In addition to these two main classes of methods, a number of other ideas and methods have been developed to increase the scope and accuracy of these two classes of methods. The review of all these methods in our presentation here is supplemented by a number numerical examples from parallel computation of complex, 3D flow problems.

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  • Aerodynamic interactions involving multiple parachute canopies

    Stein K, Benney R, Tezduyar T, Kumar V, Sathe S, Thornburg E, Kyle C, Nonoshita T

    16th AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar    2001年  [査読有り]

  • Aerodynamic and fluid-structure interactions of multiple parachute canopies

    Tezduyar T, Kumar V, Sathe S, Stein K, Benney R, Thornburg E, Kyle C, Nonoshita T

    American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   424 2   127 - 139  2001年  [査読有り]

  • A moving Lagrangian interface technique for flow computations over fixed meshes

    M Cruchaga, D Celentano, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   191 ( 6-7 ) 525 - 543  2001年  [査読有り]

     概要を見る

    In this paper, an enhanced finite element formulation for unsteady incompressible flows with moving interfaces is presented. The weak form of the Navier-Stokes equations, written using a generalized streamline operator technique, is coupled with the movement of the interface between two immiscible fluids defined through an independent moving mesh. The position of the interface is updated using a Lagrangian formulation. In this framework, a global mass conservation corrector algorithm and an enhanced element integration technique are proposed to improve accuracy. The method is applied to a number of test problems with moving interfaces. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI

  • Temporal evolution of the near wake of an impulsively started parachute canopy

    Johari H, Stein K, Tezduyar T

    Fluids 2000 Conference and Exhibit    2000年  [査読有り]

  • Stabilized-finite-element/interface-capturing technique for parallel computation of unsteady flows with interfaces

    S Aliabadi, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 243 - 261  2000年  [査読有り]

     概要を見る

    We present the stabilized-finite-element/interface-capturing (SFE/IC) method developed for parallel computation of unsteady flow problems with two-fluid interfaces and free surfaces. The SFE/IC method involves stabilized formulations, an interface-sharpening technique, and the enforcement of global mass conservation for each fluid. The SFE/IC method has been efficiently implemented on the GRAY T3E parallel supercomputer. A number of 2D test problems are presented to demonstrate how the SFE/IC method works and the accuracy it attains. We also show how the SFE/IC method can be very effectively applied to 3D simulation of challenging flow problems, such as two-fluid interfaces in a centrifuge tube and operational stability of a partially filled tanker truck driving over a bump. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • A parallel 3D computational method for fluid-structure interactions in parachute systems

    Kalro, V, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 321 - 332  2000年  [査読有り]

     概要を見る

    We present a parallel finite element computational method for 3D simulation of fluid-structure interactions (FSI) in parachute systems. The how solver is based on a stabilized finite element formulation applicable to problems involving moving boundaries and governed by the Navier-Stokes equations of incompressible flows. The structural dynamics (SD) solver is based on the total Lagrangian description of motion, with cable and membrane elements. The nonlinear equation system is solved iteratively, with a segregated treatment of the fluid and SD equations. The large linear equation systems that need to be solved at every nonlinear iteration are also solved iteratively. The parallel implementation is accomplished using a message-passing programming environment. As a test case, the method is applied to computation of the equilibrium configuration of an anchored ram-air parachute placed in an air stream. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • Parachute fluid-structure interactions: 3-D computation

    K Stein, R Benney, Kalro, V, TE Tezduyar, J Leonard, M Accorsi

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 373 - 386  2000年  [査読有り]

     概要を見る

    We present a parallel computational strategy for carrying out 3-D simulations of parachute fluid-structure interaction (FSI), and apply this strategy to a round parachute. The strategy uses a stabilized space-time finite element formulation for the fluid dynamics (FD), and a finite element formulation derived from the principle of virtual work for the structural dynamics (SD). The fluid-structure coupling is implemented over compatible surface meshes in the SD and FD meshes. Large deformations of the structure are handled in the FD mesh by using an automatic mesh moving scheme with remeshing as needed. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • Fourth Japan-US Symposium on Finite Element Methods in Large-Scale Computational Fluid Dynamics - Preface

    TE Tezduyar, TJR Hughes

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 241 - 241  2000年  [査読有り]

  • Fluid-structure interaction modeling of the US army personnel parachute system

    Benney R.J, Stein K.R, Tezduyar T.E, Accorsi M.L, Zhang W, Leonard J

    Modeling and Simulation Technologies Conference    2000年  [査読有り]

  • Fluid-object interactions in interior ballistics

    SE Ray, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 363 - 372  2000年  [査読有り]

     概要を見る

    A fluid-object interaction model for an interior ballistics problem is presented. The fluid is a compressible gas and is modeled using the Deformable-Spatial-Domain/Stabilized-Space-Time (DSD/SST) formulation. The objects can move axially within the model domain, and their motion is determined by the fluid pressure forces and collisions with other objects and rigid boundaries. The model is implemented assuming axisymmetry of the geometry and the flow field. The fluid mesh is composed of structured regions of quadrilateral elements and unstructured regions of triangular elements. The structured elements are used near the surface of the objects in order to better resolve the boundary layer, while the unstructured elements are used elsewhere in the domain. As the objects move, the mesh deformation needed to accommodate these motions takes place only in the unstructured parts of the mesh. Application to an interior ballistics problem is presented and discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • Finite element stabilization parameters computed from element matrices and vectors

    TE Tezduyar, Y Osawa

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 411 - 430  2000年  [査読有り]

     概要を見る

    We propose new ways of computing the stabilization parameters used in the stabilized finite element methods such as the streamline-upwind/Petrov-Galerkin (SUPG) and pressure-stabilizing/Petrov-Galerkin (PSPG) formulations. The parameters are computed based on the element-level matrices and vectors, which automatically take into account the local length scales, advection held and the Reynolds number. We describe how we compute these parameters in the context of first a time-dependent advection diffusion equation and then the Navier-Stokes equations of unsteady incompressible flows. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • EDICT for 3D computation of two-fluid interfaces

    TE Tezduyar, S Aliabadi

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 403 - 410  2000年  [査読有り]

     概要を見る

    We present the 3D implementation and applications of the enhanced-discretization interface-capturing technique (EDICT) in computation of unsteady flows with two-fluid interfaces. In such computations, EDICT can be used as a very effective method, which combines the flexibility and efficiency of interface-capturing techniques with the accuracy provided by enhanced discretization at the interfaces. A stabilized finite element interface-capturing technique is used as the base formulation to solve, over a typically nonmoving mesh, the Navier-Stokes equations and an advection equation governing the interface function. To increase the accuracy in modeling the interfaces, we use finite element functions with multiple components at and near the interfaces, with each component coming from a different level of mesh refinement. With its parallel implementation on advanced high-performance computing platforms such as the CRAY T3E, EDICT is a powerful tool for the simulation of a complex, 3D unsteady how problems with two fluid-interfaces, including free surfaces. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • A parallel 3D computational method for fluid-structure interactions in parachute systems

    Kalro, V, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   190 ( 3-4 ) 321 - 332  2000年  [査読有り]

     概要を見る

    We present a parallel finite element computational method for 3D simulation of fluid-structure interactions (FSI) in parachute systems. The how solver is based on a stabilized finite element formulation applicable to problems involving moving boundaries and governed by the Navier-Stokes equations of incompressible flows. The structural dynamics (SD) solver is based on the total Lagrangian description of motion, with cable and membrane elements. The nonlinear equation system is solved iteratively, with a segregated treatment of the fluid and SD equations. The large linear equation systems that need to be solved at every nonlinear iteration are also solved iteratively. The parallel implementation is accomplished using a message-passing programming environment. As a test case, the method is applied to computation of the equilibrium configuration of an anchored ram-air parachute placed in an air stream. (C) 2000 Elsevier Science S.A. All rights reserved.

    DOI

  • Methods for parallel computation of complex flow problems

    T Tezduyar, Y Osawa

    PARALLEL COMPUTING   25 ( 13-14 ) 2039 - 2066  1999年12月  [査読有り]

     概要を見る

    This paper is an overview of some of the methods developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM) [http://www, mems, rice. edu/TAFSM/] to support flow simulation and modeling in a number of "Targeted Challenges". The "Targeted Challenges" include unsteady flows with interfaces, fluid-object and fluid-structure interactions, airdrop systems, and air circulation and contaminant dispersion. The methods developed include special numerical stabilization methods for compressible and incompressible flows, methods for moving boundaries and interfaces, advanced mesh management methods, and multi-domain computational methods. We include in this paper a number of numerical examples from the simulation of complex flow problems. (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI

  • The Shear-Slip Mesh Update Method

    M Behr, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   174 ( 3-4 ) 261 - 274  1999年05月  [査読有り]

     概要を見る

    The Shear-Slip Mesh Update Method, designed to handle certain classes of how problems with moving boundaries and interfaces, is presented. Specifically, we focus on problems with large but regular boundary displacements, such as straight-line translation or rotation. These motions are accommodated by using a thin layer of deforming space-time elements, together with limited remeshing without any projection at space-time slab interfaces. As examples, 2D flow around two counter-rotating squares and 3D flow past a propeller are presented. (C) 1999 Elsevier Science S.A. All rights reserved.

    DOI

  • Parallel computational methods for flow simulation and modeling - Preface

    TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   174 ( 3-4 ) 259 - 259  1999年05月  [査読有り]

    DOI

  • Multi-domain parallel computation of wake flows

    Y Osawa, Kalro, V, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   174 ( 3-4 ) 371 - 391  1999年05月  [査読有り]

     概要を見る

    We present a new, multi-domain parallel computational method for simulation of unsteady flows involving a primary object, a long wake region and, possibly, a secondary object affected by the wake flow. The method is based on the stabilized finite element formulation of the time-dependent Navier-Stokes equations of incompressible flows. In the multi-domain computational method the entire simulation domain is divided into an ordered sequence of overlapping subdomains. The flow data computed over the leading subdomain is used for specifying the inflow boundary conditions for the next subdomain. The subdomain corresponding to the wake would not involve any objects, hence the mesh constructed over this domain would be structured. A special-purpose finite element implementation for structured meshes is used for the wake domain to achieve much higher computational speeds compared to a general-purpose implementation. We present verification studies for the multi-domain method and special-purpose implementation, followed by two numerical examples. The first example is the wake behavior behind a circular cylinder. The second one is the aerodynamic effect of tip vortices released from a leading wing on a trailing wing placed in the far wake. (C) 1999 Elsevier Science S.A. All rights reserved.

    DOI

  • CFD methods for three-dimensional computation of complex flow problems

    TE Tezduyar

    JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS   81   97 - 116  1999年05月  [査読有り]

     概要を見る

    This paper provides an overview of some of the CFD methods developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM) [http://www.mems.rice.edu/TAFSM/]. The paper also provides many examples of three-dimensional flow simulations carried out with these CFD methods and advanced parallel supercomputers. The methods and tools described in this paper include: stabilized finite element formulations; formulations for flows with moving boundaries and interfaces; mesh update methods; iterative solution techniques for large nonlinear equation systems; and parallel implementation of these methods. Our target is to be able to address effectively certain classes of flow simulation problems. These include: unsteady flows with interfaces; fluid-object interactions; fluid-structure interactions; airdrop systems; aerodynamics of complex shapes; and contaminant dispersion. (C) 1999 Elsevier Science Ltd. All rights reserved.

    DOI

  • Parallel finite element method utilizing the mode splitting and sigma coordinate for shallow water flows

    K Kashiyama, Y Ohba, T Takagi, M Behr, T Tezduyar

    COMPUTATIONAL MECHANICS   23 ( 2 ) 144 - 150  1999年03月  [査読有り]

     概要を見る

    Parallel finite element method for the analysis of quasi-three dimensional shallow water flow is presented. The mode splitting technique and the sigma coordinate (generalized coordinate) are employed to use parallel computers effectively. Parallel implementation of the unstructured grid-based formulation is carried out on the Hitachi parallel-super computer SR2201. The tidal flow of Tokyo Bay is simulated for a numerical example. The speed-up ratio and the efficiency of the parallelization are investigated. The present method is shown to be a useful and powerful tool for the large scale computation of shallow water flows.

    DOI

  • Parallel finite element computation of free-surface flows

    Guler, I, M Behr, T Tezduyar

    COMPUTATIONAL MECHANICS   23 ( 2 ) 117 - 123  1999年03月  [査読有り]

     概要を見る

    In this paper we present parallel 2D and 3D finite element computation of unsteady, incompressible free-surface flows. The computations are based on the Deformable-Spatial-Domain/Stabilized Space-Time (DSD/SST) finite element formulation, which takes automatically into account the motion of the free surface. The free-surface height is governed by a kinematic free-surface condition, which is also solved with a stabilized formulation. The meshes consist of triangles in 2D and triangular-based prism elements in 3D. The mesh update is achieved with general or special-purpose mesh moving schemes. As examples, 2D flow past spillway of a dam and 3D flow past a surface-piercing circular cylinder are presented.

    DOI

  • Parallel computation of unsteady compressible flows with the EDICT

    S Mittal, S Aliabadi, T Tezduyar

    COMPUTATIONAL MECHANICS   23 ( 2 ) 151 - 157  1999年03月  [査読有り]

     概要を見る

    Recently, the Enhanced-Discretization Interface-Capturing Technique (EDICT) was introduced for simulation of unsteady flow problems with interfaces such as two-fluid and free-surface flows. The EDICT yields increased accuracy in representing the interface. Here we extend the EDICT to simulation of unsteady viscous compressible flows with boundary/shear layers and shock/expansion waves. The purpose is to increase the accuracy in selected regions of the computational domain. An error indicator is used to identify these regions that need enhanced discretization. Stabilized finite-element formulations are employed to solve the Navier-Stokes equations in their conservation law form. The finite element functions corresponding to enhanced discretization are designed to have two components, with each component coming from a different level of mesh refinement over the same computational domain. The primary component comes from a base mesh. A subset of the elements in this base mesh are identified for enhanced discretization by utilizing the error indicator. A secondary, more refined, mesh is constructed by patching together the second-level meshes generated over this subset of elements, and the second component of the functions comes from this mesh. The subset of elements in the base mesh that form the secondary mesh may change from one time level to other depending on the distribution of the error in the computations.

    DOI

  • Advances in parallel computing methods for fluid mechanics - Editorial

    TE Tezduyar, G Yagawa

    COMPUTATIONAL MECHANICS   23 ( 2 ) 97 - 97  1999年03月  [査読有り]

  • Advanced mesh generation and update methods for 3D flow simulations

    AA Johnson, TE Tezduyar

    COMPUTATIONAL MECHANICS   23 ( 2 ) 130 - 143  1999年03月  [査読有り]

     概要を見る

    Advanced mesh generation and update methods for parallel 3D computation of complex flow problems are presented. The complexities of the class of problems targeted include complex geometries, unsteady behavior, and moving boundaries and interfaces, such as those encountered in fluid-object interactions. Parallel 3D simulation of 1000 spheres falling in a liquid-filled tube, and other computations, are presented in this paper to demonstrate the challenges involved in this class of flow problems and the methods developed to address these challenges.

    DOI

  • Space-time finite element method for shallow water flows considering moving boundaries

    Kashiyama K, Sugano S, Behr M, Tezduyar T.E

    Proceedings of the 1999 3rd ASME/JSME Joint Fluids Engineering Conference, FEDSM'99, San Francisco, California, USA, 18-23 July 1999 (CD-ROM)    1999年  [査読有り]

  • Fluid-structure interaction simulation of a cross parachute: Comparison of numerical predictions with wind tunnel data

    Stein K, Benney R, Tezduyar T, Kalro V, Potvin J, Bretl T

    15th Aerodynamic Decelerator Systems Technology Conference     172 - 181  1999年  [査読有り]

  • Advanced computational methods for 3D simulation of parafoils

    Tezduyar T, Kalro V, Garrard W

    15th Aerodynamic Decelerator Systems Technology Conference     77 - 87  1999年  [査読有り]

  • 3D Simulation and Visualization of Unsteady Wake Flow behind a Cylinder

    Osawa Y, Tezduyar T

    Journal of Visualization   2 ( 2 ) 127 - 134  1999年  [査読有り]

  • 3-D computation of parachute fluid-structure interactions: Performance and control

    Stein K, Benney R, Tezduyar T, Kalro V, Leonard J, Accorsi M

    15th Aerodynamic Decelerator Systems Technology Conference     99 - 109  1999年  [査読有り]

  • Parallel simulation of two-phase flow problems using the finite element method

    S Aliabadi, K Shujaee, T Tezduyar

    FRONTIERS '99 - THE SEVENTH SYMPOSIUM ON THE FRONTIERS OF MASSIVELY PARALLEL COMPUTATION, PROCEEDINGS     113 - 120  1999年  [査読有り]

     概要を見る

    Parallel computation of unsteady, two-phase flow problems are performed using stabilized finite element method. The finite element formulations are written for fix meshes and are based on the Navier-Stokes equations and an advection equation governing the motion of the interface function. The interface function, with two distinct values serve as an marker identifying each fluid. This function is advected with fluid velocity through out the computational domain. To increase the accuracy of the method, an interface sharpening/mass conservation algorithm is designed. The method has been implemented on the GRAY T3E and also IBM SP/6000 using the MPI libraries. We show the effectiveness of the method in simulating complex 3D problems, such as two-fluid interface in a centrifuge tube, operation stability of a partially-filled tanker truck driving over a bump and hydrodynamics stability of ships.

    DOI

  • A unified finite element formulation for compressible and incompressible flows using augmented conservation variables

    S Mittal, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   161 ( 3-4 ) 229 - 243  1998年08月  [査読有り]

     概要を見る

    A unified approach to computing compressible and incompressible Bows is proposed. The governing equation for pressure is selected based on the local Mach number. In the incompressible limit the divergence-free constraint on velocity field determines the pressure, while it is the equation of state that governs the pressure solution for the compressible flows. Stabilized finite element formulations, based on the space-time and semi-discrete methods, with the 'augmented' conservation variables are employed. The 'augmented' conservation variables consist of the usual conservation variables and pressure as an additional variable. The formulation is applied to various test problems involving steady and unsteady flows over a large range of Mach and Reynolds numbers. (C) 1998 Elsevier Science S.A. All rights reserved.

    DOI

  • Physics based GMRES preconditioner for compressible and incompressible Navier-Stokes equations

    N Nigro, M Storti, S Idelsohn, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   154 ( 3-4 ) 203 - 228  1998年03月  [査読有り]

     概要を見る

    This paper presents the implementation of a local physics preconditioning mass matrix [8] for an unified approach of 3D compressible and incompressible Navier-Stokes equations using an SUPG finite element formulation and GMRES implicit solver. During the last years a lot of effort has been dedicated to finding a unified approach for compressible and incompressible flow in order to treat fluid dynamic problems with a very wide range of Mach and Reynolds numbers [10,26,37]. On the other hand, SUPG finite element formulation and GMRES implicit solver is one of the most robust combinations to solve state of the art CFD problems [1,6,9,22,29,30,31].
    The selection of a good preconditioner and its performance on parallel architecture is another open problem in CFD community. The local feature of the preconditioner presented here means that no communication among processors is needed when working on parallel architectures. Due to these facts we consider that this research can make some contributions towards the development of a unified fluid dynamic model with high rates of convergence for any combination of Mach and Reynolds numbers, being very suitable for massively parallel computations.
    Finally, it is important to remark that while this kind of preconditioning produces stabilized results in nearly incompressible regimes the standard version exhibits some numerical drawbacks that lead to solutions without physical meaning. (C) 1998 Elsevier Science S.A.

    DOI

  • Enhanced-Discretization Interface-Capturing Technique (EDICT) for computation of unsteady flows with interfaces

    T Tezduyar, S Aliabadi, M Behr

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   155 ( 3-4 ) 235 - 248  1998年03月  [査読有り]

     概要を見る

    We present the Enhanced-Discretization Interface-Capturing Technique (EDICT) for computation of unsteady flow problems with interfaces, such as two-fluid and free-surface flows. In EDICT, we solve, over a non-moving mesh, the Navier-Stokes equations together with an advection equation governing the evolution of an interface function with two distinct values identifying the two fluids. The starting point for the spatial discretization of these equations are the stabilized finite element formulations which possess good stability and accuracy properties.
    To increase the accuracy in modeling the interfaces, we use finite element functions corresponding to enhanced discretization at and near the interface. These functions are designed to have multiple components, with each component coming from a different level of mesh refinement over the same computational domain. The primary component of the functions for Velocity and pressure comes from the base mesh called Mesh-1. A subset of the elements in Mesh-1 are identified to be at or near the interface, and depending on where the interface is, this subset could change from one time level to another. A Mesh-2 is constructed by patching together the second-level meshes generated over this subset of elements, and the second component of the functions for velocity and pressure comes from Mesh-2. For the interface function, we have a third component coming from a Mesh-3 which is constructed by patching together the third-level meshes generated over a subset of elements in Mesh-2.
    With parallel computation of the test problems presented here, we demonstrate that the EDICT can be used very effectively to increase the accuracy of the base finite element formulations. (C) 1998 Elsevier Science S.A.

    DOI

  • Parallel iterative computational methods for 3D finite element flow simulations

    Kalro V, Tezduyar T

    Computer Assisted Mechanics and Engineering Sciences   5 ( 2 ) 173 - 183  1998年  [査読有り]

  • 3D computation of unsteady flow past a sphere with a parallel finite element method

    Kalro, V, T Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   151 ( 1-2 ) 267 - 276  1998年01月  [査読有り]

     概要を見る

    We present parallel computation of 3D, unsteady, incompressible flow past a sphere. The Navier-Stokes equations of incompressible flows are solved using a stabilized finite element formulation. Equal-order interpolation functions are used for velocity and pressure. The second-order accurate time-marching within the solution process is carried out in an implicit fashion. The coupled, nonlinear equations generated at each time step are solved using an element-vector-based iteration technique. The computed value of the primary frequency associated with vortex shedding is in close agreement with experimental measurements. The computation was performed on the Thinking Machines CM-5.

    DOI

  • Parallel implementations of a finite element formulation for fluid-structure interactions in interior flows

    SE Ray, GP Wren, TE Tezduyar

    PARALLEL COMPUTING   23 ( 9 ) 1279 - 1292  1997年09月  [査読有り]

     概要を見る

    In this paper, shared-memory parallel implementations of a finite element formulation for unsteady interior flows with fluid-structure interactions are presented. The parallel computing platforms targeted are the CRAY C90, the Silicon Graphics (SGI) ONYX and the SGI Power Challenge. The formulation is based on the stabilized space-time finite element method developed earlier for a more general class of flow problems involving moving boundaries and interfaces. The specific rest problem used in the performance evaluations involves fluid-structure interactions between a barotropic working fluid and one of the two pistons surrounding this fluid. We demonstrate that advanced formulations applicable to complex problems can be implemented in a parallel computing environment without resulting in a significant distraction from the scientific objectives of solving such complex problems. (C) 1997 Elsevier Science B.V.

    DOI

  • Parallel computing methods in applied fluid mechanics

    TE Tezduyar, TJR Hughes

    PARALLEL COMPUTING   23 ( 9 ) 1215 - 1215  1997年09月  [査読有り]

    DOI

  • Parallel computational methods for 3D simulation of a parafoil with prescribed shape changes

    T Tezduyar, Kalro, V, W Garrard

    PARALLEL COMPUTING   23 ( 9 ) 1349 - 1363  1997年09月  [査読有り]

     概要を見る

    In this paper we describe parallel computational methods for 3D simulation of the dynamics and fluid dynamics of a parafoil with prescribed, time-dependent shape changes. The mathematical model is based on the time-dependent, 3D Navier-Stokes equations governing the incompressible flow around the parafoil and Newton's law of motion governing the dynamics of the parafoil, with the aerodynamic forces acting on the parafoil calculated from the flow field. The computational methods developed for these 3D simulations include a stabilized space-time finite element formulation to accommodate for the shape changes, special mesh generation and mesh moving strategies developed for this purpose, iterative solution techniques for the large, coupled nonlinear equation systems involved, and parallel implementation of all these methods on scalable computing systems such as the Thinking Machines CM-5. As an example, we report 3D simulation of a flare maneuver in which the parafoil velocity is reduced by pulling down the flaps. This simulation requires solution of over 3.6 million coupled, nonlinear equations at every time step of the simulation. (C) 1997 Elsevier Science B.V.

    DOI

  • Parallel 3D computation of unsteady flows around circular cylinders

    Kalro, V, T Tezduyar

    PARALLEL COMPUTING   23 ( 9 ) 1235 - 1248  1997年09月  [査読有り]

     概要を見る

    In this article we present parallel 3D finite element computation of unsteady incompressible flows around circular cylinders. We employ stabilized finite element formulations to solve the Navier-Stokes equations on a thinking machine CM-5 supercomputer. The time integration is based on an implicit method, and the coupled, nonlinear equations generated every time step are solved iteratively, with an element-vector based evaluation technique, This strategy enables us to carry out these computations with millions of coupled, nonlinear equations, and thus resolve the flow features in great detail. At Reynolds number 300 and 800, our results indicate strong 3D features arising from the instability of the columnar vortices forming the Karman street. At Re = 10,000 we employ a large eddy simulation (LES) turbulence model. (C) 1997 Elsevier Science B.V.

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  • Simulation of flow problems with moving mechanical components, fluid-structure interactions and two-fluid interfaces

    GP Wren, SE Ray, SK Aliabadi, TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) 1433 - 1448  1997年06月  [査読有り]

     概要を見る

    The application of a stabilized space-time finite element formulation to problems involving fluid-structure interactions and two-fluid interfaces is discussed. Two sample problems are presented and the method is validated by comparison with a test problem. (C) 1997 by John Wiley & Sons, Ltd.

    DOI

  • SPECIAL ISSUE: Third US-Japan Symposium on Finite Element Methods in Large-Scale Computational Fluid Dynamics - Preface

    TE Tezduyar, TJR Hughes

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) R3 - R3  1997年06月  [査読有り]

    DOI

  • Parallel finite element simulation of large ram-air parachutes

    Kalro, V, S Aliabadi, W Garrard, T Tezduyar, S Mittal, K Stein

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) 1353 - 1369  1997年06月  [査読有り]

     概要を見る

    In the near future, large ram-air parachutes are expected to provide the capability of delivering 21 ton payloads from altitudes as high as 25,000 ft. In development and test and evaluation of these parachutes the size of the parachute needed and the deployment stages involved make high-performance computing (HPC) simulations a desirable alternative to costly airdrop tests. Although computational simulations based on realistic, 3D, time-dependent models will continue to be a major computational challenge, advanced finite element simulation techniques recently developed for this purpose and the execution of these techniques on HPC platforms are significant steps in the direction to meet this challenge. In this paper, two approaches for analysis of the inflation and gliding of ram-air parachutes are presented. In one of the approaches the point mass flight mechanics equations are solved with the time-varying drag and lift areas obtained from empirical data This approach is limited to parachutes with similar configurations to those for which data are available. The other approach is 3D finite element computations based on the Navier-Stokes equations governing the airflow around the parachute canopy and Newton's law of motion governing the 3D dynamics of the canopy, with the forces acting on the canopy calculated from the simulated flow held. At the earlier stages of canopy inflation the parachute is modelled as an expanding box, whereas at the later stages, as it expands, the box transforms to a parafoil and glides. These finite element computations are carried out on the massively parallel supercomputers GRAY T3D and Thinking Machines CM-5, typically with millions of coupled, non-linear finite element equations solved simultaneously at every time step or pseudo-time step of the simulation. (C) 1997 by John Wiley & Sons, Ltd.

    DOI

  • Parallel finite element methods for large-scale computation of storm surges and tidal flows

    K Kashiyama, K Saitoh, M Behr, TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) 1371 - 1389  1997年06月  [査読有り]

     概要を見る

    Massively parallel finite element methods for large-scale computation of storm surges and tidal flows are discussed here. The finite element computations, carried out using unstructured grids, are based on a three-step explicit formulation and on an implicit space-time formulation. parallel implementations of these unstructured grid-based formulations are carried out on the Fujitsu Highly Parallel Computer AP1000 and on the Thinking Machines CM-5. Simulations of the storm surge accompanying the Ise-Bay typhoon in 1959 and of the tidal flow in Tokyo Bay serve as numerical examples. The impact of parallelization on this type of simulation is also investigated. The present methods are shown to be useful and powerful tools for the analysis of storm surges and tidal flows. (C) 1997 by John Wiley & Sons, Ltd.

    DOI

  • Parallel finite element computation of missile aerodynamics

    WB Sturek, S Ray, S Aliabadi, C Waters, TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) 1417 - 1432  1997年06月  [査読有り]

     概要を見る

    A flow simulation tool, developed by the authors at the Army HPC Research Center, for compressible flows governed by the Navier-Stokes equations is used to study missile aerodynamics at supersonic speeds, high angles of attack and for large Reynolds numbers. The goal of this study is the evaluation of this Navier-Stokes computational technique for the prediction of separated flow fields around high-length-to-diameter (L/D) bodies. In particular, this paper addresses two issues: (i) turbulence modelling with a finite element computational technique and (ii) efficient performance of the computational technique on two different multiprocessor mainframes, the Thinking Machines CM-5 and GRAY T3D. The paper first provides a discussion of the Navier-Stokes computational technique and the algorithm issues for achieving efficient performance on the CM-5 and T3D. Next, comparisons are shown between the computation and experiment for supersonic ramp flow to evaluate the suitability of the turbulence model. Following that, results of the computations for missile flow fields are shown for laminar and turbulent viscous effects. (C) 1997 by John Wiley & Sons, Ltd.

    DOI

  • Parallel computation of incompressible flows with complex geometries

    AA Johnson, TE Tezduyar

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   24 ( 12 ) 1321 - 1340  1997年06月  [査読有り]

     概要を見る

    We present our numerical methods for the solution of large-scale incompressible flow applications with complex geometries. These methods include a stabilized finite element formulation of the Navier-Stokes equations, implementation of this formulation on parallel architectures such as the Thinking Machines CM-5 and the GRAY T3D, and automatic 3D mesh generation techniques based on Delaunay-Voronoi methods for the discretization of complex domains. Ail three of these methods are required for the numerical simulation of most engineering applications involving fluid flow.
    We apply these methods to the simulation of airflow past an automobile and fluid-particle interactions. The simulation of airflow past an automobile is of very large scale with a high level of detail and yielded many interesting airflow patterns which help in understanding the aerodynamic characteristics of such vehicles. (C) 1997 by John Wiley & Sons, Ltd.

    DOI

  • 3D simulation of fluid-particle interactions with the number of particles reaching 100

    AA Johnson, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   145 ( 3-4 ) 301 - 321  1997年06月  [査読有り]

     概要を見る

    A high performance computing research tool has been developed for 3D simulation of fluid-particle interactions with the number of particles reaching 100. The tool is based on a stabilized space-time finite element formulation for moving boundaries and interfaces and parallel computing. Other components of this tool include: fast automatic mesh generation with structured layers of elements around the particles and unstructured meshes elsewhere; an automatic mesh moving method combined with remeshing as needed; accurate and efficient projection of the solution between the old and new meshes after each remesh; surface mesh refinement as two spheres or a sphere and the tube wall get close; and multi-platform computing.
    We apply this tool to the simulation of two cases involving 101 spheres falling in a liquid-filled tube. In both cases the initial distribution of the spheres in the tube is random. In the first simulation the size of the spheres is also random, whereas in the second case it is uniform. We demonstrate that the tool developed can be used for simulation of this class of problems with computing durations kept at acceptable levels.

    DOI

  • Simulation of compressible fluid-elastic solid interactions

    Ray S.E, Wren G.P, Tezduyar T.E

    35th Aerospace Sciences Meeting and Exhibit     1 - 11  1997年  [査読有り]

  • Parallel finite element simulation of the flare maneuver of large ram-air parachutes

    Kalro V, Garrard W, Tezduyar T

    14th Aerodynamic Decelerator Systems Technology Conference     19 - 26  1997年  [査読有り]

    DOI

  • Parallel computation of parachute fluid-structure interactions

    Stein K.R, Benney R.J, Kalro V, Johnson A.A, Tezduyar T.E

    14th Aerodynamic Decelerator Systems Technology Conference     277 - 284  1997年  [査読有り]

    DOI

  • Fluid-particle simulations reaching 100 particles

    Johnson Andrew A, Tezduyar Tayfun E

    American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED   18  1997年  [査読有り]

  • Flow simulation and high performance computing

    T Tezduyar, S Aliabadi, M Behr, A Johnson, Kalro, V, M Litke

    COMPUTATIONAL MECHANICS   18 ( 6 ) 397 - 412  1996年10月  [査読有り]

     概要を見る

    Flow simulation is a computational tool for exploring science and technology involving flow applications. It can provide cost-effective alternatives or complements to laboratory experiments, field tests and prototyping. Flow simulation relies heavily on high performance computing (HPC). We view HPC as having two major components. One is advanced algorithms capable of accurately simulating complex, real-world problems. The other is advanced computer hardware and networking with sufficient power, memory and bandwidth to execute those simulations. While HPC enables dow simulation, flow simulation motivates development of novel HPC techniques. This paper focuses on demonstrating that flow simulation has come a long way and is being applied to many complex, real-world problems in different fields of engineering and applied sciences, particularly in aerospace engineering and applied fluid mechanics. Flow simulation has come a long way because HPC has come a long way. This paper also provides a brief review of some of the recently-developed HPC methods and tools that has played a major role in bringing flow simulation where it is today. A number of 3D flow simulations are presented in this paper as examples of the level of computational capability reached with recent HPC methods and hardware. These examples are, flow around a fighter aircraft, flow around two trains passing in a tunnel,large ram-air parachutes, flow over hydraulic structures, contaminant dispersion in a model subway station, airflow past an automobile, multiple spheres falling in a liquid-filled tube, and dynamics of a paratrooper jumping from a cargo aircraft.

    DOI

  • Flow simulation and high performance computing

    T Tezduyar, S Aliabadi, M Behr, A Johnson, Kalro, V, M Litke

    COMPUTATIONAL MECHANICS   18 ( 6 ) 397 - 412  1996年10月  [査読有り]

     概要を見る

    Flow simulation is a computational tool for exploring science and technology involving flow applications. It can provide cost-effective alternatives or complements to laboratory experiments, field tests and prototyping. Flow simulation relies heavily on high performance computing (HPC). We view HPC as having two major components. One is advanced algorithms capable of accurately simulating complex, real-world problems. The other is advanced computer hardware and networking with sufficient power, memory and bandwidth to execute those simulations. While HPC enables dow simulation, flow simulation motivates development of novel HPC techniques. This paper focuses on demonstrating that flow simulation has come a long way and is being applied to many complex, real-world problems in different fields of engineering and applied sciences, particularly in aerospace engineering and applied fluid mechanics. Flow simulation has come a long way because HPC has come a long way. This paper also provides a brief review of some of the recently-developed HPC methods and tools that has played a major role in bringing flow simulation where it is today. A number of 3D flow simulations are presented in this paper as examples of the level of computational capability reached with recent HPC methods and hardware. These examples are, flow around a fighter aircraft, flow around two trains passing in a tunnel,large ram-air parachutes, flow over hydraulic structures, contaminant dispersion in a model subway station, airflow past an automobile, multiple spheres falling in a liquid-filled tube, and dynamics of a paratrooper jumping from a cargo aircraft.

    DOI

  • Simulation of multiple spheres falling in a liquid-filled tube

    AA Johnson, TE Tezduyar

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   134 ( 3-4 ) 351 - 373  1996年08月  [査読有り]

     概要を見る

    A new 3D finite element how simulation capability for fluid-particle interactions is presented and applied to study time-dependent behavior of multiple spheres falling in a liquid-filled tube. This capability is based on the flow simulation strategies such as stabilized space-time formulation for moving boundaries and interfaces, automatic mesh generation with structured layers of elements around the spheres, automatic mesh moving with remesh only as needed, and the implementation of these strategies on massively parallel computing platforms.
    Several cases of multiple spheres falling in a liquid-filled tube are studied, with the number of spheres ranging from two to five. In all cases, depending on the number of spheres and their initial arrangement, a stable state is eventually reached with all spheres arranged in a pattern corresponding to that stable state, and with all of them falling with the same terminal velocity.

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  • SPACE-TIME FINITE-ELEMENT COMPUTATION OF COMPRESSIBLE FLOWS BETWEEN MOVING COMPONENTS

    GP WREN, SE RAY, SK ALIABADI, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   21 ( 10 ) 981 - &  1995年11月  [査読有り]

     概要を見る

    A numerical simulation capability for the injector flow of a regenerative liquid propellant gun (RLPG) is presented. The problem involves fairly complex geometries and two pistons in relative motion; therefore a stabilized space-time finite element formulation developed earlier and capable of handling flows with moving mechanical components is used. In addition to the specifics of the numerical method, its application to a 30 mm RLPG test firing is discussed. The computational data from the simulation of this test case are interpreted to provide information on flow characteristics, with emphasis on the tendency of the flow to separate from the injection orifice boundary of the test problem. In addition, the computations provided insight into the behaviour of the flow entering the combustion chamber.

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  • PARALLEL FLUID-DYNAMICS COMPUTATIONS IN AEROSPACE APPLICATIONS

    SK ALIABADI, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   21 ( 10 ) 783 - 805  1995年11月  [査読有り]

     概要を見る

    Massively parallel finite element computations of the compressible Euler and Navier-Stokes equations using parallel supercomputers are presented. The finite element formulations are based on the conservation variables and the streamline-upwind/Petrov-Galerkin (SUPG) stabilization method is used to prevent potential numerial oscillations due to dominant advection terms. These computations are based on both implicit and explicit methods and their parallel implementation assumes that the mesh is unstructured. The implicit computations are based on iterative strategies. Large-scale 3D problems are solved using a matrix-free iteration technique which reduces the memory requirements significantly. The flow problems we consider typically come from aerospace applications, including those in 3D and those involving moving boundaries interacting with boundary layers and shocks. Problems with fixed boundaries are solved using a semidiscrete formulation and the ones involving moving boundaries are solved using the deformable-spatial-domain/stabilized-space-time (DSD/SST) formulation.

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  • PARALLEL FINITE-ELEMENT SIMULATION OF 3D INCOMPRESSIBLE FLOWS - FLUID-STRUCTURE INTERACTIONS

    S MITTAL, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   21 ( 10 ) 933 - 953  1995年11月  [査読有り]

     概要を見る

    Massively parallel finite element computations of 3D, unsteady incompressible flows, including those involving fluid-structure interactions, are presented. The computations with time-varying spatial domains are based on the deforming spatial domain/stabilized space-time (DSD/SST) finite element formulation. The capability to solve 3D problems involving fluid-structure interactions is demonstrated by investigating the dynamics of a flexible cantilevered pipe conveying fluid. Computations of flow past a stationary rectangular wing at Reynolds number 1000, 2500 and 10(7) reveal interesting flow patterns. In these computations, at each time step approximately 3 x 10(6) non-linear equations are solved to update the flow field. Also, preliminary results are presented for flow past a wing in flapping motion. In this case a specially designed mesh moving scheme is employed to eliminate the need for remeshing. All these computations are carried out on the Army High Performance Computing Research Center supercomputers CM-200 and CM-5, with major speed-ups compared with traditional supercomputers. The coupled equation systems arising from the finite element discretizations of these large-scale problems are solved iteratively with diagonal preconditioners. In some cases, to reduce the memory requirements even further, these iterations are carried out with a matrix-free strategy. The finite element formulations and their parallel implementations assume unstructured meshes.

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  • FINITE-ELEMENT METHODS IN LARGE-SCALE COMPUTATIONAL FLUID-DYNAMICS - PREFACE

    TE TEZDUYAR, M KAWAHARA, TJR HUGHES

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   21 ( 10 ) R3 - R3  1995年11月  [査読有り]

    DOI

  • 3-STEP EXPLICIT FINITE-ELEMENT COMPUTATION OF SHALLOW-WATER FLOWS ON A MASSIVELY-PARALLEL COMPUTER

    K KASHIYAMA, H ITO, M BEHR, T TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   21 ( 10 ) 885 - 900  1995年11月  [査読有り]

     概要を見る

    Massively parallel finite element strategies for large-scale computations of shallow water flows and contaminant transport are presented. The finite element discretizations, carried out on unstructured grids, are based on a three-step explicit formulation both for the shallow water equations and for the advection-diffusion equation governing the contaminant transport. Parallel implementations of these unstructured-grid-based formulations are carried out on the Army High Performance Computing Research Center Connection Machine CM-5. It is demonstrated with numerical examples that the strategies presented are applicable to large-scale computations of various shallow water flow problems.

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  • INCOMPRESSIBLE-FLOW PAST A CIRCULAR-CYLINDER - DEPENDENCE OF THE COMPUTED FLOW-FIELD ON THE LOCATION OF THE LATERAL BOUNDARIES

    M BEHR, D HASTREITER, S MITTAL, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   123 ( 1-4 ) 309 - 316  1995年06月  [査読有り]

     概要を見る

    The influence of the location of the lateral boundaries on 2D computation of unsteady incompressible flow past a circular cylinder is investigated. The case of Reynolds number 100 is used as a benchmark, and several quantities characterizing the unsteady flow are obtained for a range of lateral boundary locations. The computations are performed with two distinct finite element formulations - space-time velocity-pressure formulation and velocity-pressure-stress formulation. We conclude that the distance between the cylinder and the lateral boundaries can have a significant effect on the Strouhal number and other flow quantities. The minimum distance at which this influence vanishes has been found to be larger than what is commonly assumed.

    DOI

  • Parallel finite element computation of the dynamics of large ram air parachutes

    Aliabadi S.K, Garrard W.L, Kalro V, Mittal S, Tezduyar T.E, Stein K.R

    13th AIAA Aerodynamic Decelerator Systems Technology Conference     278 - 293  1995年  [査読有り]

    DOI

  • Inflation analysis of ram air inflated gliding parachutes

    Garrard W.L, Tezduyar T.E, Aliabadi S.K, Kalro V, Luker J, Mittal S

    13th AIAA Aerodynamic Decelerator Systems Technology Conference     186 - 198  1995年  [査読有り]

    DOI

  • MESH UPDATE STRATEGIES IN PARALLEL FINITE-ELEMENT COMPUTATIONS OF FLOW PROBLEMS WITH MOVING BOUNDARIES AND INTERFACES

    AA JOHNSON, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   119 ( 1-2 ) 73 - 94  1994年11月  [査読有り]

     概要を見る

    We present strategies to update the mesh as the spatial domain changes its shape in computations of how problems with moving boundaries and interfaces. These strategies are used in conjunction with the stabilized space-time finite element formulations introduced earlier for computation of flow problems with free surfaces, two-liquid interfaces, moving mechanical components, and fluid-structure and fluid-particle interactions. In these mesh update strategies, based on the special and automatic mesh moving schemes, the frequency of remeshing is minimized to reduce the projection errors and to minimize the cost associated with mesh generation and parallelization set-up. These costs could otherwise become overwhelming in 3D problems. We present several examples of these mesh update strategies being used in massively parallel computation of incompressible flow problems.

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  • MASSIVELY-PARALLEL FINITE-ELEMENT SIMULATION OF COMPRESSIBLE AND INCOMPRESSIBLE HOWS

    TE TEZDUYAR, SK ALIABADI, M BEHR, S MITTAL

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   119 ( 1-2 ) 157 - 177  1994年11月  [査読有り]

     概要を見る

    We present a review of where our research group stands in parallel finite element simulation of how problems on the Connection Machines, an effort that started for our group in the fourth quarter of 1991. This review includes an overview of our work on computation of flow problems involving moving boundaries and interfaces, such as free surfaces, two-liquid interfaces, and fluid-structure and fluid-particle interactions. With numerous examples, we demonstrate that, with these new computational capabilities, today we are at a point where we routinely solve practical flow problems, including those in 3D and those involving moving boundaries and interfaces. We solve these problems with unstructured grids and implicit methods, with some of the problem sizes exceeding 5000000 equations, and with computational speeds up to two orders of magnitude higher than what was previously available to us on the traditional vector supercomputers.

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  • IMPLEMENTATION OF IMPLICIT FINITE-ELEMENT METHODS FOR INCOMPRESSIBLE FLOWS ON THE CM-5

    JG KENNEDY, M BEHR, KALRO, V, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   119 ( 1-2 ) 95 - 111  1994年11月  [査読有り]

     概要を見る

    A parallel implementation of an implicit finite element formulation for incompressible fluids on a distributed-memory massively parallel computer is presented. The dominant issue that distinguishes the implementation of finite element problems on distributed-memory computers from that on traditional shared-memory scalar or vector computers is the distribution of data (and hence workload) to the processors and the non-uniform memory hierarchy associated with the processors, particularly the non-uniform costs associated with on-processor and off-processor memory references. Accessing data stored in a remote processor requires computing resources an order of magnitude greater than accessing data locally in a processor. This distribution of data motivates the development of alternatives to traditional algorithms and data structures designed for shared-memory computers, which must now account for distributed-memory architectures. Data structures as well as data decomposition and data communication algorithms designed for distributed-memory computers are presented in the context of high level language constructs from High Performance Fortran. The discussion relies primarily on abstract features of the hardware and software environment and should be applicable, in principle, to a variety of distributed-memory system. The actual implementation is carried out on a Connection Machine CM-5 system with high performance communication functions.

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  • MASSIVELY-PARALLEL FINITE-ELEMENT COMPUTATION OF INCOMPRESSIBLE FLOWS INVOLVING FLUID-BODY INTERACTIONS

    S MITTAL, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   112 ( 1-4 ) 253 - 282  1994年02月  [査読有り]

     概要を見る

    We describe our massively parallel finite element computations of unsteady incompressible flows involving fluid-body interactions. These computations are based on the Deforming-Spatial-Domain/Stabilized-Space-Time (DSD/SST) finite element formulation. Unsteady flows past a stationary NACA 0012 airfoil are computed for Reynolds numbers 1000, 5000 and 100000. Significantly different flow patterns are observed for these three cases. The method is then applied to computation of the dynamics of an airfoil falling in a viscous fluid under the influence of gravity. It is observed that the location of the center of gravity of the airfoil plays an important role in determining its pitch stability. Computations are reported also for simulation of the dynamics of a two-dimensional 'projectile' that has a certain initial velocity. Specially designed mesh moving schemes are employed to eliminate the need for remeshing. All these computations were carried out on the Thinking Machines CM-200 and CM-5 supercomputers, with major speed-ups compared to traditional supercomputers. The implicit equation systems arising from the finite element discretizations of these large-scale problems are solved iteratively by using the GMRES update technique with diagonal preconditioners. The finite element formulations and their parallel implementations assume unstructured meshes.

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  • FINITE-ELEMENT SOLUTION STRATEGIES FOR LARGE-SCALE FLOW SIMULATIONS

    M BEHR, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   112 ( 1-4 ) 3 - 24  1994年02月  [査読有り]

     概要を見る

    Large-scale flow simulation strategies involving implicit finite element formulations are described in the context of incompressible flows. The stabilized space-time formulation for problems involving moving boundaries and interfaces is presented, followed by a discussion of mesh moving schemes. The methods of solution of large linear systems of equations are reviewed, and an implementation of the entire finite element code, permitting the use of totally unstructured meshes, on a massively parallel supercomputer is considered. As an example, this methodology is applied to a flow problem involving three-dimensional simulation of liquid sloshing in a tank subjected to vertical vibrations.

    DOI

  • The Army High Performance Computing Research Center

    Tezduyar T.E

    IEEE Computational Science and Engineering   1 ( 2 ) 6 - 8  1994年  [査読有り]

    DOI

  • Symposium on parallel finite element computations. University of Minnesota, October 1993

    Tezduyar T.E

    Computer Methods in Applied Mechanics & Engineering   119 ( 1-2 )  1994年  [査読有り]

  • Symposium on parallel finite element computations

    Tezduyar T.E

    Computer Methods in Applied Mechanics & Engineering   119 ( 1-2 )  1994年  [査読有り]

  • Preface

    Tezduyar T.E, Mutsuto K, Hughes T.J.R

    Computer Methods in Applied Mechanics and Engineering   112 ( 1-4 )  1994年  [査読有り]

  • PARALLEL FINITE-ELEMENT COMPUTATION OF 3D FLOWS

    T TEZDUYAR, S ALIABADI, M BEHR, A JOHNSON, S MITTAL

    COMPUTER   26 ( 10 ) 27 - 36  1993年10月  [査読有り]

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  • COMPUTATION OF INCOMPRESSIBLE FLOWS WITH IMPLICIT FINITE-ELEMENT IMPLEMENTATIONS ON THE CONNECTION MACHINE

    M BEHR, A JOHNSON, J KENNEDY, S MITTAL, T TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   108 ( 1-2 ) 99 - 118  1993年09月  [査読有り]

     概要を見る

    Two implicit finite element formulations for incompressible flows have been implemented on the Connection Machine supercomputers and successfully applied to a set of time-dependent problems. The stabilized space-time formulation for moving boundaries and interfaces, and a new stabilized velocity-pressure-stress formulation are both described, and significant aspects of the implementation of these methods on massively parallel architectures are discussed. Several numerical results for flow problems involving moving as well as fixed cylinders and airfoils are reported. The parallel implementation, taking full advantage of the computational speed of the new generation of supercomputers, is found to be a significant asset in fluid dynamics research. Its current capability to solve large-scale problems, especially when coupled with the potential for growth enjoyed by massively parallel computers, make the implementation a worthwhile enterprise.

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  • SPACE-TIME FINITE-ELEMENT COMPUTATION OF COMPRESSIBLE FLOWS INVOLVING MOVING BOUNDARIES AND INTERFACES

    SK ALIABADI, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   107 ( 1-2 ) 209 - 223  1993年08月  [査読有り]

     概要を見る

    The deformable-spatial-domain / stabilized-space-time (DSD/SST) formulation, introduced by Tezduyar et al. is applied to computation of viscous compressible flows involving moving boundaries and interfaces. The stabilization technique employed is a streamline-upwind / Petrov-Galerkin (SUPG) method, with a modified SUPG stabilization matrix. The stabilized finite element formulation of the governing equations is written over the space-time domain of the problem, and therefore the deformation of the spatial domain with respect to time is taken into account automatically. The frequency of remeshing is minimized to minimize the projection errors involved in remeshing and also to increase the parallelization potential of the computations. The implicit equation systems arising from the space-time finite element discretizations are solved iteratively. It is demonstrated that the combination of the SUPG stabilization and the space-time approach gives the capability of handling complicated compressible flow problems, including those with moving surfaces and shock-boundary layer interactions.

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  • SUPG FINITE-ELEMENT COMPUTATION OF COMPRESSIBLE FLOWS WITH THE ENTROPY AND CONSERVATION VARIABLES FORMULATIONS

    GJ LEBEAU, SE RAY, SK ALIABADI, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   104 ( 3 ) 397 - 422  1993年05月  [査読有り]

     概要を見る

    SUPG-stabilized finite element formulations of compressible Euler equations based on the conservation and entropy variables are investigated and compared. The formulation based on the conservation variables consists of the formulation introduced by Tezduyar and Hughes plus a shock capturing term. The formulation based on the entropy variables is the same as the one by Hughes, Franca and Mallet, which has a shock capturing term built in. These formulations are tested on several subsonic, transonic and supersonic compressible flow problems. It is shown that the stabilized formulation based on the conservation variables gives solutions which are just as good as those obtained with the entropy variables. Furthermore, the solutions obtained using the two formulations are very close and in some cases almost indistinguishable. Consequently, it can be deduced that the relative mer-its of these two formulations will continue to remain under debate.

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  • STABILIZED FINITE-ELEMENT METHODS FOR THE VELOCITY PRESSURE STRESS FORMULATION OF INCOMPRESSIBLE FLOWS

    MA BEHR, LP FRANCA, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   104 ( 1 ) 31 - 48  1993年04月  [査読有り]

     概要を見る

    Formulated in terms of velocity, pressure and the extra stress tensor, the incompressible Navier-Stokes equations are discretized by stabilized finite element methods. The stabilized methods proposed are analyzed for a linear model and extended to the Navier-Stokes equations. The numerical tests performed confirm the good stability characteristics of the methods. These methods are applicable to various combinations of interpolation functions, including the simplest equal-order linear and bilinear elements.

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  • SUPG finite element computation of viscous compressible flows based on the conservation and entropy variables formulations

    Aliabadi S.K, Ray S.E, Tezduyar T.E

    Computational Mechanics   11 ( 5-6 ) 300 - 312  1993年  [査読有り]

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  • Numerical simulation of flows past periodic arrays of cylinders

    Johnson A.A, Tezduyar T.E, Liou J

    Computational Mechanics   11 ( 5-6 ) 371 - 383  1993年  [査読有り]

    DOI

  • NOTES ON THE STABILIZED SPACE-TIME FINITE-ELEMENT FORMULATION OF UNSTEADY INCOMPRESSIBLE FLOWS

    S MITTAL, TE TEZDUYAR

    COMPUTER PHYSICS COMMUNICATIONS   73 ( 1-3 ) 93 - 112  1992年12月  [査読有り]

     概要を見る

    This paper gives a review of our research efforts on the stabilized space-time finite element formulation of unsteady incompressible flows, including those involving moving boundaries are interfaces. Iterative solution techniques employed to solve the equation systems resulting from the space-time finite element discretization of these flow problems are also reviewed. Results are presented for certain unsteady flow problems, including large-amplitude sloshing and flows past oscillating cylinders.

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  • A FINITE-ELEMENT STUDY OF INCOMPRESSIBLE FLOWS PAST OSCILLATING-CYLINDERS AND AEROFOILS

    S MITTAL, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   15 ( 9 ) 1073 - 1118  1992年11月  [査読有り]

     概要を見る

    We present our numerical results for certain unsteady flows past oscillating cylinders and aerofoils. The computations are based on the stabilized space time finite element formulation. The implicit equation systems resulting from the space-time finite element discretizations are solved using iterative solution techniques.
    One of the problems studied is flow past a cylinder which is forced to oscillate in the horizontal direction. In this case we observe a change from an unsymmetric mode of vortex shedding to a symmetric one. An extensive study was carried out for the case in which a cylinder is mounted on lightly damped springs and allowed to oscillate in the vertical direction. In this case the motion of the cylinder needs to be determined as part of the solution, and under certain conditions this motion changes the vortex-shedding pattern of the flow field significantly. This non-linear fluid structure interaction exhibits certain interesting behaviour such as 'lock-in' and 'hysteresis', which are in good agreement with the laboratory experiments carried out by other researchers in the past. Preliminary results for flow past a pitching aerofoil are also presented.

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  • CHARACTERISTIC-GALERKIN AND GALERKIN LEAST-SQUARES SPACE-TIME FORMULATIONS FOR THE ADVECTION-DIFFUSION EQUATION WITH TIME-DEPENDENT DOMAINS

    O PIRONNEAU, J LIOU, T TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   100 ( 1 ) 117 - 141  1992年10月  [査読有り]

     概要を見る

    For the advection-diffusion equation, the characteristic-Galerkin formulations are obtained by temporal discretization of the total derivative. These formulations, by construction, are Eulerian-Lagrangian, and therefore can handle time-dependent domains without difficulty. The Galerkin/least-squares space-time formulation, on the other hand, is written over the space-time domain of a problem, and therefore can handle time-dependent domains with no implementational difficulty. The purpose of this paper is to compare these two formulations based on error estimates and numerical performance, in the context of the advection-diffusion equation.

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  • A NEW MIXED PRECONDITIONING METHOD FOR FINITE-ELEMENT COMPUTATIONS

    TE TEZDUYAR, M BEHR, SK ALIABADI, S MITTAL, SE RAY

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   99 ( 1 ) 27 - 42  1992年08月  [査読有り]

     概要を見る

    A new mixed clustered element-by-element (CEBE)/cluster companion (CC) preconditioning method for finite element computations is introduced. In the CEBE preconditioning, the elements are merged into clusters of elements, and the preconditioners are defined as series products of cluster level matrices. The CC preconditioning method, which is also introduced in this paper, shares a common philosophy with the multi-grid methods. The CC preconditioners are based on companion meshes associated with different levels of clustering. For each level of clustering, we construct a CEBE preconditioner and an associated CC preconditioner. Because these two preconditioners in a sense complement each other, when they are used in a mixed way, they can be expected to give better performance. In fact, our numerical tests, for two- and three-dimensional problems governed by the Poisson equation, demonstrate that the mixed CEBE/CC preconditioning results in convergence rates which are, in most cases, significantly better than the convergence rates obtained with the best of the CEBE and CC preconditioning methods.

    DOI

  • INCOMPRESSIBLE-FLOW COMPUTATIONS WITH STABILIZED BILINEAR AND LINEAR EQUAL-ORDER-INTERPOLATION VELOCITY-PRESSURE ELEMENTS

    TE TEZDUYAR, S MITTAL, SE RAY, R SHIH

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   95 ( 2 ) 221 - 242  1992年03月  [査読有り]

     概要を見る

    Finite element formulations based on stabilized bilinear and linear equal-order-interpolation velocity-pressure elements are presented for computation of steady and unsteady incompressible flows. The stabilization procedure involves a slightly modified Galerkin/least-squares formulation of the steady-state equations. The pressure field is interpolated by continuous functions for both the quadrilateral and triangular elements used. These elements are employed in conjunction with the one-step and multi-step time integration of the Navier-Stokes equations. The three test cases chosen for the performance evaluation of these formulations are the standing vortex problem, the lid-driven cavity flow at Reynolds number 400, and flow past a cylinder at Reynolds number 100.

    DOI

  • A NEW STRATEGY FOR FINITE-ELEMENT COMPUTATIONS INVOLVING MOVING BOUNDARIES AND INTERFACES - THE DEFORMING-SPATIAL-DOMAIN SPACE-TIME PROCEDURE .2. COMPUTATION OF FREE-SURFACE FLOWS, 2-LIQUID FLOWS, AND FLOWS WITH DRIFTING CYLINDERS

    TE TEZDUYAR, M BEHR, S MITTAL, J LIOU

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   94 ( 3 ) 353 - 371  1992年02月  [査読有り]

     概要を見る

    New finite element computational strategies for free-surface flows, two-liquid flows, and flows with drifting cylinders are presented. These strategies are based on the deforming spatial-domain/space-time (DSD/ST) procedure. In the DSD/ST approach, the stabilized variational formulations for these types of flow problem are written over their space-time domains. One of the important features of the approach is that it enables one to circumvent the difficulty involved in remeshing every time step and thus reduces the projection errors introduced by such frequent remeshings. Computations are performed for various test problems mainly for the purpose of demonstrating the computational capability developed for this class of problems. In some of the test cases, such as the liquid drop problem, surface tension is taken into account. For flows involving drifting cylinders, the mesh moving and remeshing schemes proposed are convenient and reduce the frequency of remeshing.

    DOI

  • A NEW STRATEGY FOR FINITE-ELEMENT COMPUTATIONS INVOLVING MOVING BOUNDARIES AND INTERFACES - THE DEFORMING-SPATIAL-DOMAIN SPACE-TIME PROCEDURE .1. THE CONCEPT AND THE PRELIMINARY NUMERICAL TESTS

    TE TEZDUYAR, M BEHR, J LIOU

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   94 ( 3 ) 339 - 351  1992年02月  [査読有り]

     概要を見る

    A new strategy based on the stabilized space-time finite element formulation is proposed for computations involving moving boundaries and interfaces. In the deforming-spatial-domain/space-time (DSD/ST) procedure the variational formulation of a problem is written over its space-time domain, and therefore the deformation of the spatial domain with respect to time is taken into account automatically. Because the space-time mesh is generated over the space-time domain of the problem, within each time step, the boundary (or interface) nodes move with the boundary (or interface). Whether the motion of the boundary is specified or not, the strategy is nearly the same. If the motion of the boundary is unknown, then the boundary nodes move as defined by the other unknowns at the boundary (such as the velocity or the displacement). At the end of each time step a new spatial mesh covers the new spatial domain. For computational feasibility, the finite element interpolation functions are chosen to be discontinuous in time, and the fully discretized equations are solved one space-time slab at a time.

    DOI

  • Computation of unsteady incompressible flows with the stabilized finite element methods: Space-time formulations, iterative strategies and massively parallel implementations

    Tezduyar T.E, Behr M, Mittal S, Johnson A.A

    American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   246   7 - 24  1992年  [査読有り]

  • STABILIZED FINITE-ELEMENT FORMULATIONS FOR INCOMPRESSIBLE-FLOW COMPUTATIONS

    TE TEZDUYAR

    ADVANCES IN APPLIED MECHANICS, VOL 28   28   1 - 44  1992年  [査読有り]

  • TIME-ACCURATE INCOMPRESSIBLE-FLOW COMPUTATIONS WITH QUADRILATERAL VELOCITY PRESSURE ELEMENTS

    TE TEZDUYAR, S MITTAL, R SHIH

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   87 ( 2-3 ) 363 - 384  1991年06月  [査読有り]

     概要を見る

    Quadrilateral velocity-pressure elements with constant and linear pressure interpolations are examined in the context of time-accurate finite element computation of unsteady incompressible flows. These elements involve streamline-upwind/Petrov-Galerkin stabilization and are implemented in conjunction with the one-step and multi-step temporal integration of the Navier-Stokes equations. The two test cases chosen for the performance evaluation of the formulations are the standing vortex problem and flow past a circular cylinder at Reynolds number 100.

    DOI

  • SYMPOSIUM ON RECENT DEVELOPMENTS IN LARGE-SCALE COMPUTATIONAL FLUIDS DYNAMICS - MINNESOTA-SUPERCOMPUTER-INST - MINNESOTA USA - 23-24 APRIL 1990 - PREFACE

    TE TEZDUYAR, TJR HUGHES

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   87 ( 2-3 ) 101 - 101  1991年06月  [査読有り]

  • FINITE-ELEMENT SOLUTION OF FLOW PROBLEMS WITH MIXED-TIME INTEGRATION

    GJ LEBEAU, TE TEZDUYAR

    JOURNAL OF ENGINEERING MECHANICS-ASCE   117 ( 6 ) 1311 - 1330  1991年06月  [査読有り]

     概要を見る

    A mixed-time integration method that had been developed for the finite element analysis of structural and thermal dynamics has been implemented for the study of both steady and unsteady fluid mechanics problems. The method to be discussed is capable of partitioning the domain into implicit and explicit regions in an attempt to capitalize on the desirable properties of each method, namely the stability and accuracy of the implicit method, and the manageable computational resource demands of an explicit method. In addition, the explicit region is further divided into subregions, each of which may have a different time step that is governed by the local stability criterion of an explicit method. To demonstrate the applicability of these methods to equation systems that govern fluid flow, several examples are presented. These include one- and two-dimensional advection of a cosine hill, as well as two-dimensional steady and unsteady inviscid, compressible flow problems. These examples will be used to show the favorable features of a multi-time integration method, such as a reduction in CPU time, which can be directly attributed to the differing time steps used in the various subregions.

    DOI

  • NUMERICAL-SIMULATION OF DEEP-WELL WET OXIDATION REACTOR USING STEAM

    S MITTAL, HA DEANS, TE TEZDUYAR

    JOURNAL OF ENGINEERING MECHANICS-ASCE   117 ( 4 ) 798 - 819  1991年04月  [査読有り]

     概要を見る

    A finite element model is developed for the numerical simulation of the start-up of a deep-well wet oxidation reactor using steam. The model is capable of handling different cases of start-up, using saturated steam of arbitrary quality including hot water. The transient temperature field in the well-earth system is studied. The governing equation for the earth is the conductive heat equation. For the reactor, the analysis involves solving the energy balance equations describing the convective and intertube heat transfer, mass balance equations, and thermo-dynamic relations for the fluid in the tubes. The equations for the reactor and the earth are coupled by the continuity of the temperature and heat flux at the interface between them. A Galerkin finite element formulation is used for the spatial discretization of the heat equation in the earth; a Petrov-Galerkin finite element formulation is employed for the energy balance equations in the reactor tubes. The resulting set of ordinary differential equations is discretized in time and solved by a predictor-multicorrector algorithm. The model is tested on a typical deep-well reactor to study its start-up dynamics. The results can be used to estimate the start-up time and the amount of steam or water required to obtain the necessary initiation temperature for the process.

    DOI

  • NUMERICAL EXPERIMENTS ON DOWNSTREAM BOUNDARY OF FLOW PAST CYLINDER

    TE TEZDUYAR, R SHIH

    JOURNAL OF ENGINEERING MECHANICS-ASCE   117 ( 4 ) 854 - 871  1991年04月  [査読有り]

     概要を見る

    The influence of the location of the downstream boundary on unsteady incompressible flow solutions is investigated in a series of numerical experiments performed for flow past a circular cylinder at Reynolds number 100. The governing equations are the velocity-pressure formulation of the Navier-Stokes equations, and at the downstream boundary the traction-free condition is imposed. Temporally periodic flow fields obtained by using computational domains with various lengths are compared. It is observed that as far as the near-field solution, the Strouhal number, and the lift and drag coefficients are concerned, the downstream boundary can be placed as close as 14.5 diameters from the center of the cylinder with virtually no difference in the solution. Furthermore, only third-digit variations in the Strouhal number and the lift and drag coefficients and very minor changes in the near-field solution are observed when the downstream boundary is brought as close as 6.5 diameters from the center of the cylinder. Bringing the downstream boundary closer than this seems to result in more significant changes in the solution. In particular, if the distance is 2.6 diameters or closer, the solution becomes symmetric and steady.

    DOI

  • VORTICITY STREAMFUNCTION FORMULATION OF UNSTEADY INCOMPRESSIBLE-FLOW PAST A CYLINDER - SENSITIVITY OF THE COMPUTED FLOW FIELD TO THE LOCATION OF THE OUTFLOW BOUNDARY

    M BEHR, J LIOU, R SHIH, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   12 ( 4 ) 323 - 342  1991年02月  [査読有り]

     概要を見る

    The influence of the location of the outflow computational boundary on the unsteady incompressible flow past a circular cylinder at Reynolds number 100 is examined. The vorticity-streamfunction formulation of the Navier-Stokes equations is used in all computations. Two types of outflow boundary conditions are subjected to a series of tests in which the domain length is gradually reduced. The traction-free condition performs well in most cases and allows the outflow boundary to be located as close as 6.5 cylinder diameters from the body. The other boundary condition type is not as forgiving, but has the advantage of being simpler to implement and can still provide reasonably accurate solutions. It is also observed that both condition types can influence the flow field strongly and globally when the boundary is brought closer than 2.5 diameters from the body. In such cases the temporal periodicity of the solution is lost.

    DOI

  • Wake interference behind two flat plates normal to the flow: A finite-element study

    Behr M, Tezduyar T.E, Higuchi H

    Theoretical and Computational Fluid Dynamics   2 ( 4 ) 223 - 250  1991年  [査読有り]

    DOI

  • Thermal effects on single-well chemical-tracer tests for measuring residual oil saturation

    Park Y.J, Deans H.A, Tezduyar T.E

    SPE Formation Evaluation   6 ( 3 ) 401 - 408  1991年  [査読有り]

    DOI

  • Stabilized Finite Element Formulations for Incompressible Flow Computations

    Tezduyar T.E

    Advances in Applied Mechanics   28 ( C ) 1 - 44  1991年  [査読有り]

    DOI

  • ON THE DOWNSTREAM BOUNDARY-CONDITIONS FOR THE VORTICITY-STREAM FUNCTION FORMULATION OF 2-DIMENSIONAL INCOMPRESSIBLE FLOWS

    TE TEZDUYAR, J LIOU

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   85 ( 2 ) 207 - 217  1991年01月  [査読有り]

     概要を見る

    Downstream boundary conditions equivalent to the homogeneous form of the natural boundary conditions associated with the velocity-pressure formulation of the Navier-Stokes equations are derived for the vorticity-stream function formulation of two-dimensional incompressible flows. Of particular interest are the zero normal and shear stress conditions at a downstream boundary.

    DOI

  • Finite element computation of compressible flows with the SUPG formulation

    Le Beau G.J, Tezduyar T.E

    American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED   123   21 - 27  1991年  [査読有り]

  • SOLUTION TECHNIQUES FOR THE VORTICITY-STREAMFUNCTION FORMULATION OF 2-DIMENSIONAL UNSTEADY INCOMPRESSIBLE FLOWS

    TE TEZDUYAR, J LIOU, DK GANJOO, M BEHR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   11 ( 5 ) 515 - 539  1990年10月  [査読有り]

    DOI

  • ITERATIVE ADAPTIVE IMPLICIT EXPLICIT METHODS FOR FLOW PROBLEMS

    J LIOU, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   11 ( 6 ) 867 - 880  1990年10月  [査読有り]

    DOI

  • FINITE-ELEMENT FORMULATION FOR TRANSPORT-EQUATIONS IN A MIXED COORDINATE SYSTEM - AN APPLICATION TO DETERMINE TEMPERATURE EFFECTS ON THE SINGLE-WELL CHEMICAL TRACER TEST

    YJ PARK, HA DEANS, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   11 ( 6 ) 769 - 790  1990年10月  [査読有り]

    DOI

  • COMPUTATION OF SPATIALLY PERIODIC FLOWS BASED ON THE VORTICITY STREAM FUNCTION FORMULATION

    TE TEZDUYAR, J LIOU

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   83 ( 2 ) 121 - 142  1990年10月  [査読有り]

    DOI

  • FINITE-ELEMENT SIMULATION OF DEEP-WELL WET-OXIDATION REACTOR

    J LIOU, HA DEANS, TE TEZDUYAR

    JOURNAL OF ENGINEERING MECHANICS-ASCE   116 ( 8 ) 1780 - 1797  1990年08月  [査読有り]

    DOI

  • INCOMPRESSIBLE-FLOW COMPUTATIONS BASED ON THE VORTICITY STREAM FUNCTION AND VELOCITY PRESSURE FORMULATIONS

    TE TEZDUYAR, J LIOU, DK GANJOO

    COMPUTERS & STRUCTURES   35 ( 4 ) 445 - 472  1990年  [査読有り]

    DOI

  • ADAPTIVE IMPLICIT EXPLICIT FINITE-ELEMENT ALGORITHMS FOR FLUID-MECHANICS PROBLEMS

    TE TEZDUYAR, J LIOU

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   78 ( 2 ) 165 - 179  1990年01月  [査読有り]

    DOI

  • A NEW FORMULATION FOR NUMERICAL-SIMULATION OF ELECTROPHORESIS SEPARATION PROCESSES

    DK GANJOO, TE TEZDUYAR, WD GOODRICH

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   75 ( 1-3 ) 515 - 530  1989年10月  [査読有り]

    DOI

  • FINITE-ELEMENT FORMULATION FOR THE VORTICITY-STREAM FUNCTION FORM OF THE INCOMPRESSIBLE EULER EQUATIONS ON MULTIPLY-CONNECTED DOMAINS

    TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   73 ( 3 ) 331 - 339  1989年08月  [査読有り]

    DOI

  • GROUPED ELEMENT-BY-ELEMENT ITERATION SCHEMES FOR INCOMPRESSIBLE-FLOW COMPUTATIONS

    TE TEZDUYAR, J LIOU

    COMPUTER PHYSICS COMMUNICATIONS   53 ( 1-3 ) 441 - 453  1989年05月  [査読有り]

    DOI

  • Thermal effects on single-well chemical tracer tests for measuring residual oil saturation

    Park Y.O.J, Deans H.A, Tezduyar T.E

    Society of Petroleum Engineers of AIME, (Paper) SPE   GAMMA  1989年  [査読有り]

  • Finite element computations and experimental studies of flow past an array of plates

    Higuchi H, Liou J, Behr M, Tezduyar T.E

    American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   176   45 - 54  1989年  [査読有り]

  • PETROV GALERKIN METHODS ON MULTIPLY CONNECTED DOMAINS FOR THE VORTICITY STREAM FUNCTION FORMULATION OF THE INCOMPRESSIBLE NAVIER-STOKES EQUATIONS

    TE TEZDUYAR, R GLOWINSKI, J LIOU

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   8 ( 10 ) 1269 - 1290  1988年10月  [査読有り]

    DOI

  • Adaptive implicit-explicit finite element algorithms for fluid mechanics problems

    Tezduyar T.E, Liou J

    American Society of Mechanical Engineers, Applied Mechanics Division, AMD   95   163 - 184  1988年  [査読有り]

  • Block-iterative finite element computations for incompressible flow problems

    Tezduyar T.E, Glowinski R, Liou J, Nguyen T, Poole S

    Proceedings of the International Conference on Supercomputing   Part F130184   284 - 294  1988年  [査読有り]

    DOI

  • PETROV-GALERKIN FORMULATIONS FOR ELECTROCHEMICAL PROCESSES

    DK GANJOO, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   65 ( 1 ) 61 - 83  1987年11月  [査読有り]

    DOI

  • FINITE-ELEMENT PROCEDURES FOR TIME-DEPENDENT CONVECTION DIFFUSION REACTION SYSTEMS

    TE TEZDUYAR, YJ PARK, HA DEANS

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   7 ( 10 ) 1013 - 1033  1987年10月  [査読有り]

    DOI

  • FINITE DEFORMATION OF A CIRCULAR ELASTIC MEMBRANE CONTAINING A CONCENTRIC RIGID INCLUSION

    TE TEZDUYAR, LT WHEELER, L GRAUX

    INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS   22 ( 1 ) 61 - 72  1987年  [査読有り]

    DOI

  • DISCONTINUITY-CAPTURING FINITE-ELEMENT FORMULATIONS FOR NONLINEAR CONVECTION-DIFFUSION-REACTION EQUATIONS

    TE TEZDUYAR, YJ PARK

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   59 ( 3 ) 307 - 325  1986年12月  [査読有り]

    DOI

  • PETROV-GALERKIN FORMULATIONS WITH WEIGHTING FUNCTIONS DEPENDENT UPON SPATIAL AND TEMPORAL DISCRETIZATION - APPLICATIONS TO TRANSIENT CONVECTION-DIFFUSION PROBLEMS

    TE TEZDUYAR, DK GANJOO

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   59 ( 1 ) 49 - 71  1986年11月  [査読有り]

    DOI

  • PETROV-GALERKIN FINITE ELEMENT METHOD FOR THE COMPRESSIBLE EULER AND NAVIER-STOKES EQUATIONS.

    Franca L.P, Harari I, Huges T.J.R, Mallet M, Shakib F, Spelce T.E, Chalot F, Tezduyar T.E

    American Society of Mechanical Engineers, Applied Mechanics Division, AMD   78   19 - 43  1986年  [査読有り]

  • PROFILES OF MINIMUM STRESS-CONCENTRATION FOR ANTIPLANE DEFORMATION OF AN ELASTIC SOLID

    LT WHEELER, TE TEZDUYAR, BH ELDIWANY

    JOURNAL OF ELASTICITY   15 ( 3 ) 271 - 282  1985年  [査読有り]

    DOI

  • ANALYSIS OF SOME FULLY-DISCRETE ALGORITHMS FOR THE ONE-DIMENSIONAL HEAT-EQUATION

    TJR HUGHES, TE TEZDUYAR

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING   21 ( 1 ) 163 - 168  1985年  [査読有り]

    DOI

  • ANALYSIS OF AXISYMMETRIC FINITE DEFORMATION MEMBRANE PROBLEMS ON THE DEC PRO 350 PERSONAL COMPUTER.

    Tezduyar T.E, Wheeler L.T

    American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP   98-5   227 - 236  1985年  [査読有り]

  • STABILITY AND ACCURACY ANALYSIS OF SOME FULLY-DISCRETE ALGORITHMS FOR THE ONE-DIMENSIONAL 2ND-ORDER WAVE-EQUATION

    TJR HUGHES, TE TEZDUYAR

    COMPUTERS & STRUCTURES   19 ( 4 ) 665 - 668  1984年  [査読有り]

    DOI

  • FINITE-ELEMENT METHODS FOR 1ST-ORDER HYPERBOLIC SYSTEMS WITH PARTICULAR EMPHASIS ON THE COMPRESSIBLE EULER EQUATIONS

    TJR HUGHES, TE TEZDUYAR

    COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING   45 ( 1-3 ) 217 - 284  1984年  [査読有り]

    DOI

  • NEW ALTERNATING DIRECTION PROCEDURES IN FINITE ELEMENT ANALYSIS BASED UPON EBE APPROXIMATE FACTORIZATIONS.

    Hughes T.J.R, Winget J, Levit I, Tezduyar T.E

    American Society of Mechanical Engineers, Applied Mechanics Division, AMD   54   75 - 109  1983年  [査読有り]

  • Streamline upwind formulations for advection-diffusion, Navier-Stokes, and first-order hyperbolic equations.

    Hughes T.J.R, Tezduyar T.E, Brooks A.N

      ( (ed.), Tokyo, Japan, Tokyo Univ. Press, 1982, Session III, p.97-104. (ISBN 0-444-86477-7) )  1982年  [査読有り]

  • FINITE-ELEMENTS BASED UPON MINDLIN PLATE-THEORY WITH PARTICULAR REFERENCE TO THE 4-NODE BILINEAR ISOPARAMETRIC ELEMENT

    TJR HUGHES, TE TEZDUYAR

    JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME   48 ( 3 ) 587 - 596  1981年  [査読有り]

  • FINITE ELEMENTS BASED UPON MINDLIN PLATE THEORY WITH PARTICULAR REFERENCE TO THE FOUR-NODE BILINEAR ISOPARAMETRIC ELEMENT.

    Hughes T.J.R, Tezduyar T.E

    Journal of Applied Mechanics, Transactions ASME   48 ( 3 ) 587 - 596  1981年  [査読有り]

    DOI

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