Spanwise coherence characteristics of surface pressure field on 2-D bluff bodies

In order to clarify the mechanism of the high coherent structure of surface pressure in spanwise direction on bluff body surface, its coherence as well as cross-spectrum are evaluated for a 2-D rectangular and a 2-D hexagonal cross sections in smooth flow, in turbulent flow and in 2-D sinusoidal vertically fluctuating flow. The pressure coherence was confirmed to be higher than that of the approaching flow. It was found that the pressure fluctuation at slightly upstream from the reattaching point plays the most significant role in the evaluation of buffeting force.