The wind-shade roughness model for turbulent wall-bounded flows

POSTER

Abstract

To aid in prediction of turbulent boundary layer flows over rough surfaces, a new model is proposed to estimate hydrodynamic roughness based solely on geometric surface information. The model is based on a fluid-mechanics motivated geometric parameter called the wind-shade factor. Sheltering is included using a rapid algorithm adapted from the landscape shadow literature, while local pressure drag is estimated using a piecewise potential flow approximation. Similarly to evaluating traditional surface parameters such as skewness or average slope magnitude, the wind-shade factor is purely geometric and can be evaluated efficiently from knowing the surface elevation map and the mean flow direction. The wind-shade roughness model is applied to over 100 different surfaces available in a public roughness database and some others, and the predicted sandgrain-roughness heights are compared to measured values. Effects of various model ingredients are analyzed, and transitionally rough surfaces are treated by adding a term representing the viscous stress component.

*The authors gratefully acknowledge the roughness database hosted at the University of Southampton that provides public access to crucially important data in this field. They also thank Dr. T. Jelly for help accessing some of the surface data, and Prof. I. Marusic for valuable comments and encouraging remarks about this project. CM acknowledges the Miegunyah fellowship and the Department of Mechanical Engineering at the University of Melbourne for making a sabbatical visit there possible, as well as partial support from the Office of Naval Research (grant # N00014-21-1-2162) and AFOSR (grant # FA9550-23-1-0269)). DC and NH acknowledge the support of the Air Force Office of Scientific Research under award number FA2386-23-1-4071 (program manager: D.J. Newell, AOARD) and also support from the Australian Research Council via the Discovery and Linkage Programs.

Publication: C. Meneveau, N. Hutchins and D. Chung, "The wind-shade roughness model for turbulent wall-bounded flows" (2024), J. Fluid Mech. (submitted, under review).

Presenters

  • Charles Meneveau

    • Johns Hopkins University

Authors

  • Charles Meneveau

    • Johns Hopkins University

  • Nicholas Hutchins

    • University of Melbourne

  • Daniel Chung

    • University of Melbourne