Effects of Geometric Porosity in the Trailing Edge of a Flexible Pitching Plate

Abstract

While pitching and heaving plates have been studied extensively, the effects of geometry have only recently gained interest in the research community. Inspired by porosity present in avian feathers, this numerical investigation assesses the effects of geometric porosity on a flexible pitching plate and quantifies the effect of a geometric pore of diameter 0.07C, that transitions along the centre-line between 0.725C and 0.925C. The pore forms small and periodic secondary hairpin structures in the trailing wake, having a significant effect on the propulsive efficiency (η) at lower Strouhal numbers (St). The thrust coefficient (C t ) decreases due to the effects of the pore, and the power coefficient (C Pow ) is considered invariant to the presence of the pore. Optimised geometric pores may be useful in bio-inspired micro air vehicle applications, as well as wind and ocean engineering.