Coherent structure statistics in the wake of a sharp-edged bluff body placed vertically in a shallow channel

Abstract

Proper orthogonal decomposition and closed-streamline-based vortex identification algorithm has been applied to extract information on coherent structures downstream of a sharp-edged bluff body, placed vertically in a shallow open channel flow. The friction effect of the bed was found to reduce the size and strength of the coherent structures close to the bed. The free surface weakly decreases the size and strength of the prevalent coherent structures. The population trends of coherent structure statistics with downstream distance indicate the phenomenon of merging and spatial growth of coherent structures with time and space. But the rates of merging and growth were found to be different at different vertical locations over the flow depth. The distribution functions of the location, size and strength in the transverse direction were examined to shed light on the dynamics of these structures.