Fluctuating wall shear stress in turbulent channel flows is decomposed into small-scale and large-scale components. The large-scale fluctuating wall shear stress is computed as the footprints of the outer tur- bulent motions, and the small-scale one is obtained by subtracting the large-scale one from the total, which fully remove the outer influences. We show that the statistics of the small-scale fluctuating wall shear stress is Reynolds number independent at the friction Reynolds number larger than 1000, while which is Reynolds number dependent or the low-Reynolds-number effect exists at the friction Reynolds number smaller than 1000. Therefore, a critical Reynolds number that defines the emergence of universal small-scale fluctuating wall shear stress is proposed to be 1000. The total and large-scale fluctuating wall shear stress intensities approximately follow logarithmic-linear relationships with Reynolds number, and empirical fitting expressions are given in this work.

Limin Wang;Ruifeng Hu

Center for Particle-Laden Turbulence,Key Laboratory of Mechanics on Disaster and Environment in Western China,Ministry of Education,College of Civil Engineering and Mechanics,Lanzhou University,Lanzhou 730000,China

力学快报（英文）

[1]Limin Wang;Ruifeng Hu-.Inner-outer decomposition of wall shear stress fluctuations in turbulent channels)[J].力学快报（英文）,2022(02):132-136

bulent

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