News

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Research

Study on Universality of Subcritical Turbulent Transition in Wall Shear Flows
e.g., plane Poiseuille flow, duct flow, annular Couette flow

About...

• Mechanism of turbulent-laminar coexistence patterns generation and maintenance,

• Stochastic behavior in spatio-temporal intermittency of turbulent patterns,

• Directed percolation (DP) universality class in non-equilibrium physics 

Education and Employment

2022 Apr. -
JSPS Research Fellowship for Young Scientist DC2, Japan Society for the Promotion of Science (JSPS)

2021 Apr. -

PhD student, Dept. of Mechanical Engineering, Tokyo University of Science (TUS)

(2023 Apr. - renamed to Dept. of  Mechanical and Aerospace Engineering, TUS)

2021 Mar.

M.Eng., Dept. of Mechanical Engineering, Tokyo University of Science

2019 Mar.

B.Eng., Dept. of Mechanical Engineering, Tokyo University of Science

Committee Memberships

• 2022 Apr. - 2023 Mar.
  Committee Chair, Summer School for Young Researchers in Fluid Mechanics 2022, The Japan Society of Fluid Mechanics,  https://sites.google.com/view/ryutaiwakate2022

• 2021 Apr. - 2022 Mar.
  Deputy committee chair, Ph.D. Student Association of Noda Campus, Tokyo University of Science

Awards, Grants and Fellowships

• 2024 Jan. - Mar.
  Student Dispatch to Foreign Educational/Research Institutions,
  Tokyo University of Science
  https://www.tus.ac.jp/kokusai_program/program/graduate

• 2023 Sep.
  International Conference Dispatch Program for Ph.D. students,
  Tokyo University of Science
  https://www.tus.ac.jp/kokusai_program/program/graduate

• 2022 Apr. - 2023 Mar.
  JSPS Research Fellowship for Young Scientist DC2,
  Grants-in-Aid for Scientific Research (KAKENHI): Grant-in-Aid for JSPS Fellows 22J14598,
  Japan Society for the Promotion of Science

• 2022 Mar.
  Best Presentation Award,
  XXV Eight-inter-institutional Seminar on Turbulent Flow Control 2021

• 2021 Dec.
  Best Presentation Award for Young Researcher,
  The 35th Symposium on Computational Fluid Dynamics,
  The Japan Society of Fluid Mechanics 

• 2021 Jul.
  Repayment Exemption for Students with Excellent Grades,
  Japan Student Services Organization (JASSO) Type I (interest-free) scholarship 

• 2021 Apr. - 2022  Mar.
  Fellowship Program for Material Science Researcher,
  Tokyo University of Science 

• 2021 Mar.
  Graduate School Research Encouragement Award,
  Society of Automotive Engineers of Japan, Inc.

Publications

Journal Papers   Google Scholar

• 2022

1. Kazuki Kohyama, Masaki Sano, and Takahiro Tsukahara, "Sidewall Effect on Turbulent Band in Subcritical Transition of High-Aspect-Ratio Duct Flow ," Physics of Fluids, 34(8), 084112. [Online Journal (Open Access)]

• 2021

• 2020

1. Kazuki Takeda, Yohann Duguet, and Takahiro Tsukahara, "Intermittency and critical scaling in annular Couette flow," Entropy, 22(9), 988. [Online Journal (Open Access)]

Reports

• 2022

1. Kazuki Kohyama, Yuki Matsukawa, Kosuke Nakagawa, "Report on the Summer School for Young Fluid Researchers 2022", NAGARE ( journal of Japan Society of Fluid Mechanics published bimonthly), Vol. 41, No. 5 (2022), p. 362. (in Japanese)[Open Access]

• 2021

1. Kazuki Takeda, Hirotaka Morimatsu and Takahiro Tsukahara, “A Study on Spatio-Temporal Intermittencies and DP Universality of Turbulent Puffs: Direct Numerical Simulation of Annular Cuette-Poiseuille Flow”, SENAC PR brochure of Cyberscience Center in Tohoku University, Vol. 54, No. 4, pp. 22-33 (2021). (in Japanese) [Open Access]

• 2020

1. Takahiro Tsukahara, Kazuki Takeda, “Study of subcritical transitions in artificial extended annular flows by direct numerical simulation”, SENAC PR brochure of Cyberscience Center in Tohoku University, Vol. 53, No. 4, pp. 90-98 (2020). (in Japanese) [Open Access]

Proceedings / Seminar / Workshop (in English)

• 2023

1. Kazuki Kohyama, Turbulent-laminar coexisting structures and traveling waves in annular Couette flows at low Reynolds number, The 68th Workshop on “Investigation and Control of Transition to Turbulence”, Tokyo, Japan, Oct. 24-25 (2023).

2. Kazuki Kohyama and Takahiro Tsukahara, Reproducing turbulent puff split and decay in transitional annular flow by a two-variable stochastic model, In Proc. the 10th Int. Symp. on Turbulence, Heat & Mass Transfer (THMT10), Rome, Italy, Sep. 11-15 (2023), ID: J070.

3. Kazuki Kohyama and Takahiro Tsukahara, Turbulence maintenance limitation at low Reynolds number in annular Couette flow with very small radius ratios, In Abst. Proc. of 18th European Turbulence Conference (ETC18), Valencia, Spain, Sep. 4-6 (2023), p. 208 (ID: 504).

4. Kazuki Kohyama and Takahiro Tsukahara, Reproducing Spatio-Temporal Intermittency of Turbulent Puffs with Domany–Kinzel Model, In Abst. Proc. of 22nd International Couette-Taylor Workshop (ICTW23), Barcelona, Spain, Jun. 28-30 (2023), p. 94. 

• 2022

1. Kazuki Kohyama, Takahiro Tsukahara, Keiichi Tamai and Masaki Sano, Effect of the presence or absence of sidewalls on the subcritical transition of channel flow and the directed percolation phenomena, The 66th Workshop on “Investigation and Control of Transition to Turbulence", Tokyo, Japan, Sep. 25-26 (2022)．

2. Kazuki Kohyama, Masaki Sano, Keiichi Tamai and Takahiro Tsukahara, Directed percolation phenomena in subcritical transition of high-aspect-ratio duct flow, In  Proc. of Twelfth International Symposium on Turbulence and Shear Flow Phenomena (TSFP12), Osaka, Japan (virtual), Jul. 19-22 (2022), ID: 312.

• 2021

1. Takahiro Tsukahara, Chigusa Izumi, Yuki Matsukawa and Kazuki Takeda, Patterning of Turbulent Natural Convection in Vertical Channel, In Proc. of The 8th Asian Symposium on Computational Heat Transfer and Fluid Flow (ASCHT2021), Qingdao, China (virtual), Sep. 23-26 (2021), ASCHT2021-041.

2. Kazuki Takeda, Masaki Sano and Takahiro Tsukahara, Side-Wall Effect of High-Aspect-Ratio Duct Flow on Turbulent Bands in Subcritical Transition, In  Proc. of The 8th Asian Symposium on Computational Heat Transfer and Fluid Flow (ASCHT2021), Qingdao, China (virtual), Sep. 23-26 (2021), ASCHT2021-256.

3. Kazuki Takeda and Takahiro Tsukahara, Intermittent Turbulent Structures in Subcritical Transition of Annular Couette Flow with/without Imaginary Domain, In  Proc. of International congress of theoretical and applied mechanics 2020+1 (ICTAM2020+1), Milano, Italy (virtual), Aug. 22-27 (2021), pp. 98-99 (O108731).

• 2020

1. Kazuki Takeda, Yohann Duguet, and Takahiro Tsukahara,DNS study of annular Couette flow for low-high radius ratio in subcritical transition, In Proc. of 17th International Conference on Flow Dynamics (ICFD2020), Sendai, Japan (virtual), Oct. 28-30 (2020), pp. 448-451.

• 2019

1. Kazuki Takeda and Takahiro Tsukahara, New knowledge as DP universality class on the subcritical turbulent transitions of wall-bounded shear flows, In Abst. Proc. of 7th Asia-Pacific Congress on Computational Mechanics (APCOM2019), Taipei, Taiwan, Dec. 18-20 (2019), p. 281.

2. Kazuki Takeda and Takahiro Tsukahara, Subcritical transition of plane Poiseuille flow as DP universality classes in (2+1) and (1+1) dimensions, In Proc. of the 7th Asian Symposium on Computational Heat Transfer and Fluid Flow (ASCHT2019), Tokyo, Japan, Sep. 3-7 (2019), I112, 2 pages.

3. Kazuki Takeda and Takahiro Tsukahara, Subcritical transition of plane Poiseuille flow as (2+1)d and (1+1)d DP universality classes, 8th Symposium on Bifurcations & Instabilities in Fluid Dynamics (BIFD2019), Limerick, Ireland, Jul. 16-19 (2019).

Seminars, etc.

• 2024

1. Directed percolation universality in subcritical transition of turbulence in the wall-bounded flows, LMFA seminar, Laboratoire de Mécanique des Fluides et d’Acoustique, École Centrale de Lyon, Feb. 16 (2024)．[Invited Talk]

• 2022

2. 「博士学生支援制度（マテリアル人材フェローシップ制度）体験談」，第7回　東京理科大学 野田学生博士会  「現在(いま)の博士の話」 ～博士号取得後に活躍している社会人の“生の声”～，東京理科大学 野田キャンパス，2022年10月26日．[Invited Talk]

3. 「学振DC2 採択までの道のり」，東京理科大学 2023年度採用分日本学術振興会特別研究員（DC1,DC2），東京理科大学，2022年4月7日．[Invited Talk]

Society

• Student Member, Japan Society of Fluid Mechanics (JSFM)

• Member, The Japan Society of Mechanical Engineers (JSME)

• Member, The Physical Society of Japan (JPS)