TAKIZAWA, Kenji

写真a

Affiliation

Faculty of Science and Engineering, School of Creative Science and Engineering

Job title

Professor

Homepage URL

http://www.jp.tafsm.org/

Profile

See also http://www.jp.tafsm.org/

Concurrent Post 【 display / non-display

  • Faculty of Science and Engineering   Graduate School of Creative Science and Engineering

Research Institute 【 display / non-display

  • 2020
    -
    2022

    理工学術院総合研究所   兼任研究員

Education 【 display / non-display

  •  
    -
    2005

    Tokyo Institute of Technology   Graduate School, Division of Integrated Science and Engineering   Energy Sciences  

  •  
    -
    2002

    Tokyo Institute of Technology   Graduate School, Division of Integrated Science and Engineering   Energy Sciences  

  •  
    -
    2001

    Tokyo Institute of Technology   Faculty of Engineering   Mechano-Aerospace Engineering  

Degree 【 display / non-display

  • 2005.03   Tokyo Institute of Technology   PhD

Professional Memberships 【 display / non-display

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    Committee on Fluid-Structure Interaction, Applied Mechanics Division, ASME

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    Journal of Applied Mechanics, ASME

  •  
     
     

    Committee on Fluid-Structure Interaction, Applied Mechanics Division, ASME

  •  
     
     

    Committee on Fluid-Structure Interaction, Applied Mechanics Division, ASME

 

Research Areas 【 display / non-display

  • Fluid engineering

Research Interests 【 display / non-display

  • CSD

  • CFD

  • IGA (Isogeometric Analysis)

  • Fluid-Structure Interaction

Papers 【 display / non-display

  • Anatomically realistic lumen motion representation in patient-specific space-time isogeometric flow analysis of coronary arteries with time-dependent medical-image data

    Yu, Yuxuan, Zhang, Yongjie Jessica, Takizawa, Kenji, Tezduyar, Tayfun E., Sasaki, Takafumi

    COMPUTATIONAL MECHANICS   65 ( 2 ) 395 - 404  2020.02  [Refereed]

     View Summary

    Patient-specific computational flow analysis of coronary arteries with time-dependent medical-image data can provide valuable information to doctors making treatment decisions. Reliable computational analysis requires a good core method, high-fidelity space and time discretizations, and an anatomically realistic representation of the lumen motion. The space-time variational multiscale (ST-VMS) method has a good track record as a core method. The ST framework, in a general context, provides higher-order accuracy. The VMS feature of the ST-VMS addresses the computational challenges associated with the multiscale nature of the unsteady flow in the artery. The moving-mesh feature of the ST framework enables high-resolution flow computation near the moving fluid-solid interfaces. The ST isogeometric analysis is a superior discretization method. With IGA basis functions in space, it enables more accurate representation of the lumen geometry and increased accuracy in the flow solution. With IGA basis functions in time, it enables a smoother representation of the lumen motion and a mesh motion consistent with that. With cubic NURBS in time, we obtain a continuous acceleration from the lumen-motion representation. Here we focus on making the lumen-motion representation anatomically realistic. We present a method to obtain from medical-image data in discrete form an anatomically realistic NURBS representation of the lumen motion, without sudden, unrealistic changes introduced by the higher-order representation. In the discrete projection from the medical-image data to the NURBS representation, we supplement the least-squares terms with two penalty terms, corresponding to the first and second time derivatives of the control-point trajectories. The penalty terms help us avoid the sudden unrealistic changes. The computation we present demonstrates the effectiveness of the method.

    DOI

  • Space–Time Variational Multiscale Isogeometric Analysis of a tsunami-shelter vertical-axis wind turbine

    Yuto Otoguro, Hiroki Mochizuki, Kenji Takizawa, Tayfun E. Tezduyar

    Computational Mechanics    2020

     View Summary

    © 2020, The Author(s). We present computational flow analysis of a vertical-axis wind turbine (VAWT) that has been proposed to also serve as a tsunami shelter. In addition to the three-blade rotor, the turbine has four support columns at the periphery. The columns support the turbine rotor and the shelter. Computational challenges encountered in flow analysis of wind turbines in general include accurate representation of the turbine geometry, multiscale unsteady flow, and moving-boundary flow associated with the rotor motion. The tsunami-shelter VAWT, because of its rather high geometric complexity, poses the additional challenge of reaching high accuracy in turbine-geometry representation and flow solution when the geometry is so complex. We address the challenges with a space–time (ST) computational method that integrates three special ST methods around the core, ST Variational Multiscale (ST-VMS) method, and mesh generation and improvement methods. The three special methods are the ST Slip Interface (ST-SI) method, ST Isogeometric Analysis (ST-IGA), and the ST/NURBS Mesh Update Method (STNMUM). The ST-discretization feature of the integrated method provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. 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 blade and other turbine geometries and increased accuracy in the flow solution. The STNMUM enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex turbine geometry. The quality of the mesh generated with this method is improved with a mesh relaxation method based on fiber-reinforced hyperelasticity and optimized zero-stress state. We present computations for the 2D and 3D cases. The computations show the effectiveness of our ST and mesh generation and relaxation methods in flow analysis of the tsunami-shelter VAWT.

    DOI

  • ALE and Space–Time Variational Multiscale Isogeometric Analysis of Wind Turbines and Turbomachinery

    Yuri Bazilevs, Kenji Takizawa, Tayfun E. Tezduyar, Ming Chen Hsu, Yuto Otoguro, Hiroki Mochizuki, Michael C.H. Wu

    Modeling and Simulation in Science, Engineering and Technology     195 - 233  2020

     View Summary

    © 2020, Springer Nature Switzerland AG. Many of the challenges encountered in computational analysis of wind turbines and turbomachinery are being addressed by the Arbitrary Lagrangian–Eulerian (ALE) and Space–Time (ST) Variational Multiscale (VMS) methods and isogeometric discretization. The computational challenges include turbulent rotational flows, complex geometries, moving boundaries and interfaces, such as the rotor motion, and the fluid–structure interaction (FSI), such as the FSI between the wind turbine blade and the air. The core computational methods are the ALE-VMS and ST-VMS methods. These are supplemented with special methods like the Slip Interface (SI) method and ST Isogeometric Analysis with NURBS basis functions in time. We describe the core and special methods and present, as examples of challenging computations performed, computational analysis of horizontal- and vertical-axis wind turbines and flow-driven string dynamics in pumps.

    DOI

  • Element length calculation in B-spline meshes for complex geometries

    Otoguro, Yuto, Takizawa, Kenji, Tezduyar, Tayfun E.

    COMPUTATIONAL MECHANICS    2020.01  [Refereed]

     View Summary

    Variational multiscale methods, and their precursors, stabilized methods, have been playing a core-method role in semi-discrete and space-time (ST) flow computations for decades. These methods are sometimes supplemented with discontinuity-capturing (DC) methods. The stabilization and DC parameters embedded in most of these methods play a significant role. Various well-performing stabilization and DC parameters have been introduced in both the semi-discrete and ST contexts. The parameters almost always involve some element length expressions, most of the time in specific directions, such as the direction of the flow or solution gradient. Until recently, stabilization and DC parameters originally intended for finite element discretization were being used also for isogeometric discretization. Recently, element lengths and stabilization and DC parameters targeting isogeometric discretization were introduced for ST and semi-discrete computations, and these expressions are also applicable to finite element discretization. The key stages of deriving the direction-dependent element length expression were mapping the direction vector from the physical (ST or space-only) element to the parent element in the parametric space, accounting for the discretization spacing along each of the parametric coordinates, and mapping what has been obtained back to the physical element. Targeting B-spline meshes for complex geometries, we introduce here new element length expressions, which are outcome of a clear and convincing derivation and more suitable for element-level evaluation. The new expressions are based on a preferred parametric space and a transformation tensor that represents the relationship between the integration and preferred parametric spaces. The test computations we present for advection-dominated cases, including 2D computations with complex meshes, show that the proposed element length expressions result in good solution profiles.

    DOI

  • Isogeometric hyperelastic shell analysis with out-of-plane deformation mapping (vol 63, pg 681, 2019)

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

    COMPUTATIONAL MECHANICS   65 ( 1 ) 267 - 268  2020.01  [Refereed]

    DOI

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Books and Other Publications 【 display / non-display

  • Computational fluid-structure interaction: Methods and applications

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

    John Wiley  2013.02 ISBN: 9780470978771

  • CIP法とJavaによるCGシミュレーション

    矢部 孝, 尾形 陽一, 滝沢 研二

    森北出版  2007.02 ISBN: 9784627919112

Misc 【 display / non-display

  • 2A15 Relations among morphology, wall stress and pathology in the thoracic aorta

    SUITO Hiroshi, TAKIZAWA Kenji, TEZDUYAR Tayfun E., UEDA Takuya

      2015 ( 27 ) 309 - 309  2015.01

    CiNii

  • 2A23 Arterial Wall Modeling and Medical Image Mapping Based on Element-Based Zero-Stress State Estimation Method

    SASAKI Takafumi, TAKIZAWA Kenji, ITATANI Keiichi, TAKAGI Hirokazu, Tezduyar Tayfun E., MIYAZAKI Shohei, MIYAJI Kagami

      2015 ( 27 ) 315 - 316  2015.01

    CiNii

  • Ringsail-Parachute Fluid Mechanics Computation with Resolved Geometric Porosity

    Tsutsui Yuki, Toh Narumi, Terahara Takuya, Takizawa Kenji, Tezduyar Tayfun E., Boswell Cody

    The Computational Mechanics Conference   2014 ( 27 ) 399 - 400  2014.11

    CiNii

  • A114 An aorta dynamics computation with the element-based zero-stress state estimation method

    SASAKI Takafumi, Tezduyar Tayfun E.

    Proceedings of the ... JSME Conference on Frontiers in Bioengineering   2014 ( 25 ) 25 - 26  2014.10

    CiNii

  • Collaboration between Mathematical Science and Clinical Medicine via Computational Simulations(Essay)

    Suito Hiroshi, Takizawa Kenji, Ueda Takuya

    Journal of the Japan Society for Simulation Technology   33 ( 3 ) 231 - 233  2014.09

    CiNii

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Awards 【 display / non-display

  • The 2018 JSPS Prize

    2018.12   Japan Society for the Promotion of Science  

    Winner: TAKIZAWA, Kenji

  • 2016 NISTEP Award, Japan National Institute of Science and Technology Policy (NISTEP)

    2016.12   National Institute of Science and Technology Policy (NISTEP)  

  • Highly Cited Researcher (Engineering)

    2016.11   Thomson Reuters  

  • Japan Research Front Awards 2016

    2016.07   Thomson Reuters  

  • Young Scientists' Prize, Commendation for Science and Technology by Japan Minister of Education, Culture, Sports, Science and Technology

    2015.04  

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Research Projects 【 display / non-display

  • Fluid-Structure Interaction Modeling of Heart Valves and Red Blood Cells

    Grant-in-Aid for Scientific Research (A)

    Project Year :

    2018.04
    -
    2023.03
     

  • Advancement of HPC Applications for Manufacturing Technology to Exascale

    Grant-in-Aid for Scientific Research (S)

    Project Year :

    2014.05
    -
    2019.03
     

  • 4D Zonal Classification of Time-Periodic Flows: Formulation and Computational Methods

    Grant-in-Aid for Challenging Exploratory Research

    Project Year :

    2016.04
    -
    2018.03
     

    Kenji Takizawa

     View Summary

    To understand time-periodic flow behavior, we focus on particle residence time. Residence time can be computed with the Eulerian form of the equations, and thus can be defined over the entire domain as a time-dependent variable.
    We use aorta flow as example of pulsating inflow, and turbomachinery as a moving-boundary problem. To obtain periodic behavior of the residence time, we keep computing the time-periodic flow. The residence time at the outlet can be estimated with a simple theory and we compare that to the computed value. Residence time lower than the theoretical value implies presence of regions where the flow is not connected to the rest of the domain. Such regions can be detected with the residence time by comparing it to the computation duration. To increase the calculation accuracy, we introduced a characteristic-based method, refinement techniques, and new ways of calculating the stabilization parameters.

  • ものづくり流体アプリケーションのエクサスケールへの進化

    基盤研究(A)

    Project Year :

    2014.04
    -
    2015.03
     

    青木 尊之, 高木 知弘, 滝沢 研二, 森口 周二, 下川辺 隆史

     View Summary

    エクサスケールのスパコンにおいて、ものづくりを革新的に発展させるアプリケーションを開発するためには、既存のアプリケーションから根底から作り直す必要がある。所望する計算結果を得るまでの時間「Time to Solution」を最重要視した新しい陽的時間積分に基づいた数値計算手法と計算アルゴリズムを導入する研究を進めた。
    数値計算手法(離散化)に関して陰解法から陽解法、低次精度から高次精度空間離散化、非構造格子から局所的に均一な構造格子等への転換を行い、一方で計算アルゴリズムに対して、① データ移動の最小化、② 演算密度の向上、③ ノード間通信を隣接通信に限定等を行う。さらに詳細なパフォーマンス・モデルを構築し、エクサスケールの問題規模において高い実行性能を確実に達成する。手本となる流体アプリケーションの成功例を示し、ものづくり分野への大きな貢献を目的として研究に着手した。
    計算アルゴリズムの検討において、完全陽解法にすることで、ペタスケールの格子系アプリケーションで導入してきた演算と通信のオーバーラップによる通信時間の隠ぺいが計算の殆どの部分で可能になることを確認した。さらに、方向分離を双曲型方程式にTemporal Blockingによる時間積分方向のデータ再利用にキャッシュの利用を促進する計算アルゴリズムを導入を検討した。
    この段階で本基盤研究(A)を包含する基盤研究(S)の採択が決定し、以降の研究遂行を基盤研究(S)で行うこととした。

  • Higher-Order Space-Time Parameterization and Modeling of Fluid and Object Interaction

    Grant-in-Aid for Young Scientists (B)

    Project Year :

    2012.04
    -
    2015.03
     

    TAKIZAWA Kenji

     View Summary

    This research is aimed to establish solving fluid mechanics equations for practical engineering problems. The important point in this research is that not only modeling on spatial discretization but also temporal discretization; space and time modeling.
    There are three topics. One is smoothness of the motion, which comes from acceleration continuity in dynamics. Second one is topology change in fluid domain, such as heart valve problems. The third one is how to treat rotating objects, such as wind turbine problems.

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Syllabus 【 display / non-display

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