Model for Mixture Theory Simulation of Vortex Sand Ripple Dynamics

Abstract

The complex coupled interactions between fluid and sandy sediment on the seafloor are simulated with a three-dimensional bottom boundary layer model (SedMix3D) developed from mixture theory. SedMix3D solves the unfiltered Navier-Stokes equations for a fluid-sediment mixture treated as a single continuum with effective properties that parameterize the fluid-sediment and sediment-sediment interactions including a variable mixture viscosity, a bulk hindered settling velocity, and a shear-induced, empirically calibrated, mixture diffusion term. A sediment flux equation models the concentration of sediment by describing the balance of sediment flux by advection, gravity, and shear-induced diffusion. The grid spacing is on the order of a sediment grain diameter, and simulated flows had maximum free-stream velocities between 20 and