Questions on the effects of roughness and its analysis in non-equilibrium flows

Abstract

The prediction of turbulent flows over rough surfaces is important for many applications in engineering and in the natural sciences. Since the resolution of the roughness requires significant computational resources, most modelling approaches rely on the related concepts of ‘equivalent sand-grain roughness’ and ‘wall similarity’. While the validity of these concepts is well established for zero-pressure-gradient boundary-layers and for channel flows, such is not the case for non-equilibrium conditions. This raises a number of important questions, some of which are discussed in this paper. We also suggest some possible paths to answering these questions.

Keywords:

• Turbulent boundary layers

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

William Devenport would like to acknowledge the support of ONR (Office of Naval Research) in particular Peter Chang, Ki-Han Kim and Yin Lu Young for their support [grant numbers N00014-18-1-2455, N00014-19-1-2109 and N00014-20-1-2821]. Ugo Piomelli acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC-CRSNG), under the Discovery Grant program. Ralph Volino acknowledges the support of ONR (Office of Naval Research) [grant number N0001421WX00771] monitored by Peter Chang.