Unravelling turbulent transport on the basis of a hierarchy of coherent vortices and its prediction

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20403
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Osaka University
• Principal Investigator: Motoori Yutaro 大阪大学, 大学院基礎工学研究科, 助教 (20906911)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: 乱流 / 壁乱流 / 乱流輸送 / 渦 / 固体粒子 / 数値シミュレーション

Outline of Final Research Achievements

Turbulence is composed of coherent vortices of different sizes. In the present study, we have unraveled the physical mechanism of mass transport in turbulence based on the hierarchy of coherent vortices. In near-wall turbulence, sufficiently small particles are inhomogeneously distributed. They form clusters. More precisely, heavy particles are swept out from vortices with the eddy turnover time comparable to the particle relaxation time to form clusters around the vortices. On the other hand, light particles accumulate in the center of the vortices. Thus, the time scale match between the particle relaxation time and the eddy turnover time is an important factor for particle clustering. We have demonstrated this fact by conducting large-scale direct numerical simulations.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

乱流は身の回りにあふれた現象であるため、幅広い分野で、乱流による物質輸送の制御や予測が求められる。しかし、乱流のもつ強い非線形により、単純な場合においても、乱流輸送に関して理解されていない部分は多い。本研究では、乱流による固体粒子の輸送を、乱流の維持機構に対して重要な役割を果たす「秩序渦の階層」に基づいて、明らかにした。乱流の本質に根ざした解析であるからこそ得られた本研究の結果は明快であり、将来の乱流制御・予測に向けて、より高度な展開が期待される。