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

Abstract

In this study, we use a two-dimensional clustering methodology to identify the high-and low-speed structures of the streamwise wall-shear fluctuations in turbulent channel flows at different Reynolds numbers. The statistical properties of the high- and low-speed structures, such as geometrical characteristics, fluctuating intensities and conditional velocity fluctuations, are shown to be remarkably asymmetrical. The low-speed structures are closely related with the celebrated attached eddies. Our work may aid to the future development of the attached-eddy model.