Shallow flow past a cavity: globally coupled oscillations as a function of depth

Abstract

The structure of shallow flow past a cavity is characterized as a function of elevation above the bed (bottom surface) and the onset of coupling between the separated shear layer along the opening of the cavity and a gravity wave mode within the cavity. A technique of particle image velocimetry is employed to characterize the flow structure. Coherent patterns of vorticity along the cavity opening and at the trailing (impingement) wall of the cavity are related to the streamline topology and associated critical points as a function of elevation above the bed. Associated patterns of normal and shear Reynolds stresses are defined, and related to the exchange velocity and mass exchange coefficient along the cavity opening. Substantial increase in mass exchange between the cavity, and the main flow occurs in presence of shear layer-gravity wave coupling for all elevations above the bed.