A DNS of a Turbulent Flow in a Rough-Wall Channel Using Roughness Elements Model

A Direct Numerical Simulation (DNS) is conducted for a turbulent flow in a channel bounded by one rough and another smooth wall. Rough wall is modeled by roughness elements represented by zero-volume wall-normal lines extending 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 inteded here to demonstrate the validity of the roughness model, comparing the obtained flow with available experimental results. It was confirmed that the model reproduces the experimentally obtained mean flow satisfactorily and that turbulence modification by roughness in the layer above the top of roughness elements is qualitatively coincident with the experimental results.