Boundary Layer Adjustments to Bottom Topography and Suspended Sediment

Abstract

An accurate knowledge of flow in the immediate vicinity of the sea bed is important in marine geological, benthic ecological, geochemical, and sediment transport studies. However in many cases, the velocity field is complicated by the presence of ripples and dunes on the sea bed and suspended sediment-induced stratification in the flow. Recently techniques for handling these factors were developed by the authors, but they were applied only to a situation where the sea bed was comprised of a single size and specific gravity class. In this paper these techniques are extended to the case where the suspended material is characterized by an ensemble of settling velocities and critical shear velocities. The results are applied first to a flat sea bed and then to spatially averaged flow over a wavy boundary such as might be produced by natural bed forms. These calculations indicate that the sediment transport process can have a significant effect on flow near the sea bed and that proper account must be taken of the settling velocity distribution comprising the suspended sediment concentration field.