A DNS of a Turbulent Flow in a Channel with a Rough Wall

Abstract

A Direct Numerical Simulation (DNS) is conducted for a turbulent flow in a channel having a rough wall and a smooth wall. Rough wall is modelized by roughness elements represented by zero-volume wall-normal lines projected from the wall surface to around 15∼30 in wall unit which generate Stokes drag to the local flow. Global Reynolds number based on the mean friction velocities on two walls and channel half width is 400. It is intended here to demonstrate the validity of the roughness model, comparing the obtained flow with available experiments. It was confirmed that the model reproduces the experimentally obtained mean flow satisfactorily and that turbulence modification by roughness above the layer of roughness elements is qualitaively coincident with experiments.