Non-Hydrostatic Versus Hydrostatic Three Dimensional Simulation of Flow Separation over Bed Forms

The flow over bed forms consists of contracting flow, flow separation and expanding flow. Typically, flow separation occurs near the crest of the bed form with flow re-attachment on the adverse slope. Flow acceleration occurs on the upstream side, while flow deceleration occurs at the lee side of the crest of the bed form producing an eddy and generating localized turbulent kinetic energy. This conversion of the mean kinetic energy into turbulent kinetic energy results in additional energy losses related to form drag. In this study, multi-beam bathymetric surveys and ADCP data collected from the Lower Mississippi River by the United States Army Corps of Engineers were used to setup a set of high resolution three dimensional computer models utilizing HydroQual's Estuarine and Coastal Ocean Model ECOMSED, the Danish Hydraulic Institute's (DHI) MIKE 3 hydrodynamics flow model and Hayco's three dimensional circulation model H3D.