Abstract
Recent findings [X. Wu et al., Proc. Natl. Acad. Sci. USA 114, E5292 (2017)] reinforce earlier assertions [e.g., R. Falco, Philos. Trans. R. Soc. London A 336, 103 (1991)] 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 . Both the pocket width and time interval between pocket events increase logarithmically with Reynolds number when normalized by viscous units. Normalization of and by the Taylor microscales evaluated at a wall-normal location of about 100 viscous units, however, appears to successfully remove this Reynolds-number dependence. The present results are discussed in the context of motion formation owing to the three dimensionalization of the near-wall vorticity field and, concomitantly, the recurring perturbation of the viscous sublayer.
1 More- Received 6 August 2017
DOI:https://doi.org/10.1103/PhysRevFluids.2.124602
©2017 American Physical Society