Turbulence multi-scale interaction based on global stability of unsteady / nonequillibrium flow

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14880
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Tohoku University
• Principal Investigator: Yakeno Aiko 東北大学, 流体科学研究所, 助教 (30634331)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 乱流 / 流体制御 / 安定性解析 / 遷移 / 非モード安定性 / エネルギー過渡増幅

Outline of Final Research Achievements

I attempted to theoretically elucidate the multi-scale interaction of the flow by performing a global stability analysis of the fluid for a non-stationary and non-uniform flow field. Focusing on the energy transient amplification in the non-orthogonal mode, we succeeded in acquiring some new findings on the drag reduction of the spanwise wall oscillation and the transition delay of the boundary layer. In the spanwise wall oscillation, oblique streaks grow and the original streak weakens, which is consistent with the result of maximum transient amplification of energy. And, it was confirmed that a small oblique flow structure existed near the wall in the boundary layer, which also coincided with the maximum transient amplification mode of energy. In addition, new discoveries and proposals were made regarding the transition of the three-dimensional boundary layer of the aircraft swept wing and the transition delay effect of micro distributed roughness.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

流体機器の低抵抗化は省エネルギーやCO2排出削減を大幅に達成できるため，喫緊の最重要課題の一つである．抵抗の増加は，機器表面近くの流れの秩序運動が主原因である．これまで様々な流れの制御手法が検討されてきているが，いずれも効果が低くとどまるか実現不可能であった．一方，近年の計算機の発展により秩序運動がさらに理解が深まっている．特に支配方程式の非直交的性質による「エネルギーの過渡増幅」により，秩序の発生という世紀の問いの一つが解かれつつある．本研究成果は，基礎理論の拡張にとどまらず，実現可能な新技術の提案をさらに期待できるものである．制御概念はあらゆる流体機器に適用され社会的波及効果は莫大である．