THREE-DIMENSIONAL CALCULATION OF FLOW OVER TWO-DIMENSIONAL DUNE

Abstract

The finite amplitude growth and stability of ripples and dunes is believed to be the result of the interaction between the complex turbulence field created by separation at the crest of the bed feature and bedload sediment transport. Numerical simulation of this turbulence field promises to provide the detailed qualitative and quantitative information of coherent structures that is required to model the sediment transport field over ripples and dunes. We present a high-order Godunov scheme, referred to as the CIP method, for the numerical simulation of turbulence over a 2-dimensional dune. Comparison of the velocity statistics of the numerical simulation with LDV measurements over 2-dimensional dunes in a flume is favorable. Analysis of the vorticity field reveals that the coherent turbulent structures produced in the shear layer are highly three-dimensional, and cross-stream velocities should be considered in future models of bedload transport over dunes.