APPLICATION OF ROMS FOR SIMULATING EVOLUTION AND MIGRATION OF TIDAL SAND WAVES

A three-dimensional morphodynamic numerical sand wave model is established based on an existing model, the Regional Oceanographic Modelling System (ROMS). In the model, the vertical flow structure, which plays an important role in the formation and evolution of sand waves, is resolved by solving three dimensional (3D) Reynolds-averaged Navier-Stokes (RANS) equations with a k-epsilon turbulence closure. The bed slope effect on the bedload transport is considered in the model. The model is capable of capturing sand wave evolution and migration processes, which can not be modeled by conventional stability models. First, a sensitivity analysis of the model configuration is conducted, including the morphological factor, the time step and the grid size, to find out an optimal balance between the computational time and the accuracy of results. The effects of the water depth, flow velocity and sand grain size on the Fastest Growing Mode (FGM) are then studied. Finally, a migrating artificial sand wave is simulated and numerical results are presented.