Modeling of vortex ripple morphodynamics

Abstract

A new morphology module has been developed in order to perform simulations of the bed form evolution under hydrodynamic forcing. This module has been implemented into the numerical model Dune2D, which solves the Reynolds Averaged Navier-Stokes (RANS) equations in the boundary layer and resolves sediment transport over moving sand beds. The morphology module is composed of a modified central scheme and a routine that simulates avalanches and has been successfully applied to the study of orbital ripples evolution. Ripple growth from a quasiflat bed have been simulated, and the growth behavior has been compared to previous experimental measurements. The simulated ripples reach an equilibrium state where energy damping processes (avalanches) compensate energy production processes (flux of sediment). These processes have been analyzed during ripple creation, growth, merging, and annihilation. Furthermore, sandy bed evolutions have been simulated with random initial bed forms in order to examine the influence of the bed "history" on the final solution and the wave energy dissipated during these evolutions. Copyright 2008 by the American Geophysical Union.