Comparative Analysis of HLLC- and Roe-Based Models for the Simulation of a Dam-Break Flow in an Erodible Channel with a 90∘ Bend

Abstract

In geophysical surface flows, the sediment particles can be transported under capacity (equilibrium) conditions or noncapacity (nonequilibrium) conditions. On the one hand, the equilibrium approach for the bedload transport assumes that the actual transport rate instantaneously adapts to the local flow features. The resulting system of equations, composed of the shallow water equations for the flow (SWE) and the Exner equation for the bed evolution, has been widely used to simulate bedload processes. These capacity SWE + Exner models are highly dependent on the setup parameters, so that the calibration procedure often disguises the advantages and flaws of the numerical method. On the other hand, noncapacity approaches account for the temporal and spatial delay of the actual sediment transport rate with respect to the capacity of the flow. The importance of assuming nonequilibrium conditions in bedload numerical models remains uncertain however. In this work, we compared the performances of three different strategies for the resolution of the SWE + Exner system under capacity and noncapacity conditions to approximate a set of experimental data with fixed setup parameters. The results indicate that the discrete strategy used to compute the intercell fluxes significantly affected the solution. Furthermore, the noncapacity approach can improve the model prediction in regions with complex transient processes, but it requires a careful calibration of the nonequilibrium parameters.