Revisiting Raupach’s Flow-Sheltering Paradigm

Xiang Yang, Mingwei Ge

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5 Scopus citations


In this commentary, we revisit Raupach’s flow-sheltering paradigm that asserts reduced wall-shear stress behind a surface roughness element (MR Raupach in Boundary-Layer Meteorol, 60(4):375–395, 1992). Direct numerical simulations of a turbulent boundary layer over a wall-mounted rectangular roughness are conducted we consider roughness with three different aspect ratios and flows at two Reynolds numbers. A large computational domain is used to study the behaviours of the wall-shear stress in both the near-wake and the far-wake regions. Aside from a low wall-shear stress region in the near-wake as one would expect from the flow-sheltering paradigm, a high-stress region is found in the far-wake. The presence of such a high-stress region challenges the well-established flow sheltering paradigm and is also counter-intuitive. Detailed analysis of the vortical structures shows that the high wall-shear stress region is a consequence of the horse-shoe-vortex-induced downwash motion in the far-wake.

Original languageEnglish (US)
Pages (from-to)313-323
Number of pages11
JournalBoundary-Layer Meteorology
Issue number2
StatePublished - May 2021

All Science Journal Classification (ASJC) codes

  • Atmospheric Science


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