A two-dimensional numerical model for a turbidity current

A 2-D numerical model for flow of and deposition from a turbidity current was developed to simulate processes on a natural scale and topography for flows with sand-size sediment. The velocity of the bulk fluid (sediment + water) is calculated from a momentum equation that is derived from the Navier-Stokes equation using the hydrostatic and boundary layer approximations. Sediment concentrations are calculated with advection-diffusion equations for each grain size and turbulence is taken into account by using the Mellor-Yamada level 21/2 second-order closure model. The effect of the presence of particles on the turbulence other than through buoyancy is incorporated through a drag term that leads to an extra dissipation term in the turbulent kinetic energy equation and in the turbulent lengthscale equation. The equations are solved numerically using a finite volume method on a non-staggered grid with a BDF method. Model results are shown for two flows with different initial concentrations. showing the behaviour of the model.