Numerical Simulations on Developments of Dunes by Using Depth Averaged Model

Abstract

A numerical model to predict the formation processes of dunes in open channel flows is developed. Flows and bed shear stresses over dunes are calculated by the depth averaged model considering the effect of vertical acceleration. Inotational condition of flows far from a dune bed and the acceleration/de-acceleration effect near a bed are included in the depth averaged model. Formation processes of dunes are simulated incorporating the nonequilibrium sediment transport model proposed by Nakagawa·Tsujimoto. Calculated results on the temporal development processes and shape characteristics of dunes are compared with previous theoretical and experimental studies. It is indicated that the calculated wave length caused by initial instability is coincident with the resonant relation of open channel flows over a wavy bed, and the wave length and height of dunes in the equilibrium state are dependent on the step length.