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On the structure of streamwise wall-shear stress fluctuations in turbulent channel flows

Published online by Cambridge University Press:  28 September 2020

Cheng Cheng ,
Weipeng Li Open the ORCID record for Weipeng Li [Opens in a new window] ,
Adrián Lozano-Durán Open the ORCID record for Adrián Lozano-Durán [Opens in a new window]  and
Hong Liu
Cheng Cheng
Affiliation:
School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai200240, China
Weipeng Li*
Affiliation:
School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai200240, China
Adrián Lozano-Durán
Affiliation:
Center for Turbulence Research, Stanford University, Stanford, CA94305, USA
Hong Liu
Affiliation:
School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai200240, China
*
†Email address for correspondence: liweipeng@sjtu.edu.cn
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Abstract

A growing body of studies in wall-bounded turbulence has shown that the generation of wall-shear stress fluctuations is directly connected with outer-layer large-scale motions. In the present study, we investigate the scale-based structures of the streamwise wall-shear stress fluctuations ($\tau _x'$) in turbulent channel flows at different Reynolds numbers. The wall-shear stress structures are identified using a two-dimensional clustering methodology, and two indispensable factors, scale and sign, are considered for the analysis. The structures are classified into positive and negative families according to the sign of $\tau _x'$. The statistical properties of the structures, including geometrical characteristics, spatial distribution, population density, fluctuating intensity, and correlations with outer motions are comprehensively investigated. Particular attention is paid to the asymmetries between positive and negative structures and their connection with wall-attached energy-containing eddies. In virtue of our results, only the large-scale structures of negative $\tau _x'$ contain the footprints of the inactive part of wall-attached eddies populating the logarithmic region.

JFM classification

Boundary Layers: Boundary layer structure Turbulent Flows: Turbulent boundary layers
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 903 , 25 November 2020 , A29
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Copyright
© The Author(s), 2020. Published by Cambridge University Press

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References

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