Experimental study on the mechanism of large-scale structure in wall turbulence

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13683
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Nagoya University
• Principal Investigator: Iwano Koji 名古屋大学, 工学研究科, 助教 (20750285)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 乱流境界層 / 大規模構造 / バースト現象 / 抵抗低減

Outline of Final Research Achievements

n this study, artificial large-scale structures were introduced into the boundary layer using the plasma actuators in a wind tunnel with the aim of clarifying the generation and maintenance mechanisms of the large-scale structure in the turbulent boundary layer. The velocity fluctuations in the buffer region and the logarithmic region were measured simultaneously using a multi-point hot wire anemometer. As a result, it was found that the burst frequency in the buffer region is scaled using the local friction velocity of the large-scale structure. This suggests that the small-scale vortices near the wall are unilaterally influenced by the large-scale structure, and that the large-scale structure is likely to be maintained independently of the small-scale vortices.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

壁乱流の構造を理解し制御することは，工学の様々な分野において重要である．本研究では，壁面摩擦の大部分を生み出す壁近傍の小規模渦は，境界層内に存在する大規模構造の影響を一方向的に受けており，大規模構造は小規模渦の存在に頼らず維持されている可能性が高いことが明らかとなった．これは大規模渦を制御することにより，壁面摩擦を低減させることができる可能性を示唆するものであり，工学的に重要な知見である．