Investigation of drag reduction through a flapping mechanism on circular cylinder

During flapping wing, a bird develops sufficient lift force as well as counteracts drag and increases its speed through different orientations of feathers on the flapping wings. Differently oriented feathers play a significant role in drag reduction during flying of a bird. With an objective to investigate the effect of installation of such flapping mechanism as a mean of drag reduction in case of flow over circular cylinder, this concept has been implemented through installation of continuous and mini flaps, made of MS sheet metal, where flaps are oriented at different angles as like feathers of flapping wings. The experiments are carried out in a subsonic wind tunnel. After validation and comparison with conventional result of drag analysis of a single cylinder, effects of flapping with Reynolds number variation, implementation of different orientations of mini flaps and variation of different interspacing distance between mini flaps are studied to find the most effective angle of attack of drag reduction on the body of circular cylinder. This research show that, installation of continuous flap reduces value of drag co-efficient, CD up to 66%, where as mini flaps are found more effective by reducing it up to 73%. Mini flaps of L/s=6.25, all angled at 30O, at the 30O angular position on the body of circular cylinder has been found the most effective angle of attack for drag reduction in case of flow over circular cylinder.