LARGE-EDDY SIMULATION OF OSCILLATORY FLOW, SEDIMENT TRANSPORT AND MORPHODYNAMICS OVER RIPPLES

In the present study, a well-resolved large-eddy simulation was coupled to a morphodynamical model in order to study the sediment dynamics induced by an oscillatory flow over a sandy bed, as well as the creation/evolution of ripples under hydrodynamic forcing. The simulations were based on the numerical solution of the Navier-Stokes equations for the flow, empirical formulas for the bed load, and the advection-diffusion equation for the suspended sediment. The evolution of the bed form was obtained by the numerical solution of the conservation of sediment mass equation. The Immersed Boundary method was implemented for the imposition of fluid and sediment boundary conditions on the moving bed surface. The model was effectively validated against laboratory measurements. Results are presented for ripple creation and propagation from a quasi-flat bed, as well as results of ripples adapting to water conditions.