The effects of leading edge orientation on the aerodynamic performance of dragon fly wing section in gliding flight

Abstract

In this work, we investigate the aerodynamic characteristics and spatio-temporal dynamics of a wing cut section of dragon fly (Aeshna Cyanea) at ultra-low Reynolds number corresponding to the gliding flight of this dragon fly. The simulations employ an unstructured triangular mesh based on finite volume discretization. A critical assessment of the computed results is performed. Numerical simulations are performed at ultra-low Reynolds number of 10,000 at different angles of attack. Three insect wing sections are modelled with different orientation of the leading edge. It is shown that among all profiles, Profile LEU has largest gliding ratio at higher angles of attack. The larger gliding ratio is due to the fact that the overall drag coefficient is smaller as compared to other Profiles LES and LED. The smaller drag coefficient is due to the presence of large negative shear regions present in the flow. The negative shear regions are because of vortices formed attached to the leading edge or inside the pleats. The presence of vortices attached not only reduces the contribution of shear drag but pressure drag also.