Implicit Large-Eddy Simulations of Rough-Wall Turbulent Channel FLows

Abstract

A rough wall layer modeling approach is developed for implicit large-eddy simulations (ILES) of high Reynolds number turbulent flows over rough walls. The fluid dynamics of the averaged flow in the near-wall rough layer is modeled using the Brinkman equation, while the outer free flow region is resolved using ILES. Fully developed turbulent channel flows with rod and mesh roughness on both walls are calculated. The computational results of the mean streamwise velocity, fluctuating velocity, one-dimensional streamwise energy spectra, and the three-dimensional instantaneous flow structures are presented. The results show that the present rough wall layer modeling approach for ILES predicts well the log-law mean velocity, and fluctuating velocity profiles in the outer layer region. The flow structures indicate that complex three-dimensional incoherent spanwise vortical structures are formed. The quasi-streamwise structures formed above the roughness elements are locally interrupted by modeled roughness effects or other incoherent structures, and as a result, a high-energy layer is developed above the roughness elements.