Reynolds number scaling of pocket events in the viscous sublayer

Abstract

Recent findings [X. Wu et al., Proc. Natl. Acad. Sci. USA 114, E5292 (2017)10.1073/pnas.1704671114] reinforce earlier assertions [e.g., R. Falco, Philos. Trans. R. Soc. London A 336, 103 (1991)10.1098/rsta.1991.0069] that the sublayer pocket motions play a distinctly important role in near-wall dynamics. In the present study, smoke visualization and axial velocity measurements are combined in order to establish the scaling behavior of pocket events in the viscous sublayer of the turbulent boundary layer. In doing so, an identical analysis methodology is employed over an extensive range of friction Reynolds numbers 388≤δ+≤2.2×105. Both the pocket width W and time interval between pocket event..