Wall boundary conditions for rough walls (Q2641659)

Summary: The treatment of rough walls is still a considerable challenge in computational fluid dynamics. Empirical wall functions are available to bridge the flow and shear stress in the near-wall computational cells to the wall distance and roughness. The concept of equivalent sand-grain roughness has been applied. In the present paper, we present a near-wall flow model that uses the concept of equivalent sand-grain roughness height. A simple and fast numerical solution procedure is used to produce the necessary input for the wall treatment in the momentum and turbulence field transport equations. In particular, we try to make a link between real roughness geometry and the equivalent roughness height. Typical applications of the presented wall treatment are industrial applications like friction in multiphase pipelines and velocity distribution over complex terrain, in conjunction with localisation of windmills.