Feedback control for turbulence based on coherent vortex structure

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K14883
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Akita University
• Principal Investigator: SASAKI Eiichi 秋田大学, 理工学研究科, 助教 (60710811)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 秩序渦 / スパース性 / 数値解

Outline of Final Research Achievements

In turbulence, we could find coherent vortex structures, suggesting that the intrinsic degrees of freedom of turbulence are smaller than the degrees of freedom of the system, such as the number of grid points. We call this property sparse. We have considered sparse representation for turbulence.
We examined the reconstruction method for box turbulence and found that the velocity field could be reconstructed using 30% of the total grid points. For plane-Couette turbulence, we obtained unstable periodic orbits describing the generation of spanwise vortex structures. We conducted the wind tunnel experiment and established velocimetry using pitot tubes and heat wires. Moreover, we performed flow visualization using smoke and laser sheet light sources.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

乱流運動には秩序渦が存在する．この事実は乱流の本質的な自由度が格子点数など系の自由度に比べ圧倒的に少ないことを示唆する．秩序渦の動力学に関する研究が多くなされてきたが，スパース性を用いた乱流運動の解析や推定は行われていなかった．本研究で，素朴なスパース推定法によって限られた測定点の情報から流れ場を再構成できることが分かった．Couette乱流について新たな秩序渦の動力学を見出した．渦運動に立脚した推定法が必要であることが示された．