Numerical simulation of the temporal evolution of a three dimensional barchanoid dune and the corresponding sediment dynamics

In this paper we present the results of the numerical simulation of a three-dimensional current-driven sediment transport process. In detail, the temporal evolution of a barchanoid dune is studied. Two phenomena are treated in this context. First, the three-dimensional flow of a single phase fluid is considered. Second, the interaction of the flow and the sediment bed with its morphological change of the sediment surface is taken into account. We numerically solve the instationary incompressible Navier-Stokes equations, an advection diffusion equation and Exner's bed level equation to update the sediment bed morphology. Here, Exner's equation determines the change of the bed level due to the bed load. The suspended material is treated as a sediment concentration and its movement is modelled by an advection-diffusion equation. To secure the continuous interchange between bed load and the suspension load sink and source terms are used. Both equations are discretised and explicitly coupled to the discrete fluid model. The typical sedimentary processes and the sedimentary form of a prototypical barchanoid dune are well captured by our numerical simulation, which is supported by a qualitative comparison with examples from the literature.