A full three dimensional numerical simulation of the sediment transport and the scouring at a rectangular obstacle

•A three dimensional model for current-driven sediment processes.•Loose partitioned coupled algorithm for the fluid and sediment interaction.•A numerical simulation of a scour mark and their morphology.•Qualitative comparison with laboratory work from a flume.

We employ a numerical simulation of the three-dimensional fluid flow and the simultaneous transport of sediment to reproduce current-driven sediment transport processes. In particular, the scouring at a rectangular obstacle is investigated. To solve the instationary incompressible Navier–Stokes equations we use the code NaSt3D. The morphological change of the sediment bed is modeled by Exner’s bed level equation, which is discretized and coupled to the discrete fluid model, i.e., to the NaSt3D code. A large eddy turbulence approach using a Smagorinsky subgrid scale tensor is applied. For our purposes, we only consider bed load transport under clear water conditions. Furthermore, we demonstrate mass conservation and convergence of our approach for a test case. We compare the results of our numerical simulations for a scour mark with those obtained in a laboratory flume. The typical sedimentary processes and the sedimentary form of a scour mark are well captured by our numerical simulation.