Modeling Sediment-Laden Gravity Currents

The gravity currents formed by instantaneous releases of a fixed volume of a suspension of fine sediment into a rectangular channel filled with tap water are studied numerically. The numerical model based on the filtered Navier-Stokes equations and mass transport equation is used to model dynamics of the flow and sediment transport. The effects of subgrid eddies on flow and sediment transport were calculated based on the modified Smagorinsky model that takes into account the effect of buoyancy on turbulence. The sediment transport is computed by the dispersion model. The governing equations are solved based on the operator-splitting algorithm and the third-order CCS scheme, which employs the Crank-Nicolson scheme for time advancing and the cubic spline to fit the spatial distributions of physical variables such as velocity components and concentration. Such a numerical scheme has been proven stable and almost free of numerical diffusion. The paper presents the comparisons between the numerical results and the experimental data such as propagation speed and areal sediment deposit. It is found that the numerical model is capable of correctly reproducing the flows and the associated sediment transport processes.