A computational study of the hydrodynamic forces on a rough wall
The hydrodynamic interaction of a fluid with a rough wall results in a net force on the roughness elements. This can cause erosion of the roughness elements – an important aspect for sediment transport in rivers or the transport of solid media by fluids in mechanical applications. In order to deepen the understanding of the processes that lead to erosion, a direct numerical simulation of a turbulent open channel flow over a fixed rough bed was carried out. In the simulation spherical roughness elements were discretized by means of the immersed boundary method developed by .
The flow field statistics of the simulation compare well to data of previous studies with respect to the mean flow field as well as the turbulence statistics . Furthermore, the instantaneous flow field exhibits the expected formations of streaks and of large structures that extent over the entire water depth as well as the formation of smaller coherent structures.