Sediment Transport over Ripples in Oscillatory Flow

In this paper, we present results of a large-eddy simulation of flow and suspended sediment transport around prototypical ripples based on "long-wave ripples" as measured at Duck, N.C., in waves of height 1 m and period of 10 s. Solving the volume-filtered Navier-Stokes equations for the momentum and an advection-diffusion equation with a setting term for the suspended sediment, we obtain time-dependent, three-dimensional descriptions of the velocity, pressure, and sediment concentration fields. Although the main flow and sediment transport patterns are governed by a quasi-two-dimensional vortex formation-ejection mechanism, we illustrate the three-dimensional structure of both, and make qualitative comparisons with the results of other researchers. We conclude with analysis of concentration time series measured at a point and interpret them within the larger framework of the flow. The present simulations demonstrate that the flow over these larger-scale ripples resembles that over vortex ripples quite strongly.