Experimental investigation on the flow over normal flat plates with various corner shapes

Abstract

The influence of corner modification on the flow over normal flat plates is experimentally investigated in a water tunnel. Particle image velocimetry measurement is performed at Re = 2240 based on the width of the plate. Besides the flat plate with sharp edges, others with chamfered corners, rounded corners and stepped corners at the windward side are studied. Although the flat plate is very thin compared with square cylinders, corner modification can also achieve a significant drag reduction. The mechanism for the drag reduction is explored based on the solid analysis of the vortical structures and the statistical parameters. With corner modification, the strength and the scale of the vortex are decreased, while the formation of the vortex is postponed, resulting in a weakened vortex-interaction process. Thus, the fluctuation intensity of the wake is weakened, the wake width is narrowed down with the recirculation region elongated, and the vortex shedding frequency becomes higher. These modifications interpret well how the drag of a normal plate could be reduced, which is confirmed by the drag estimation from the wake profiles.