One-Dimensional Riemann Solver Involving Variable Horizontal Density to Compute Unsteady Sediment Transport

Abstract

Intense transient shallow flows over erodible bed imply the appearance of a changing horizontal density attributable to the presence of sediment particles in the water layer. The lack of consideration of the variability of the bulking density of the mixture is not admissible when modeling severe types of erosional flow such as the release of a dam break wave over a sedimentary bottom. Such events can lead to significant changes in the wave hydrodynamics, since the inertia of the flow can be larger and consequently its erosion/deposition capacity can be altered. From a numerical point of view a new complex erosion/deposition source term appears. For the integration of these source terms two strategies have been explored in this work: upwind and pointwise. Hence, this work is focused on the development and validation of a novel numerical scheme based on an approximate augmented Riemann solver, where the erosion/deposition rates play an important role in the variation of mixture density. Several analytical test cases have been derived in order to validate the computational tool. The numerical predictions have also been compared against experimental data.