Effect of leading-edge curvature on the aerodynamics of insect wings

The aerodynamic performance of an insect wing is largely dependent on the leading-edge vortex (LEV) on the wing formed during the rotational translation phase of its flapping motion. The geometry of the wing can directly influence the formation and strength of the LEV. The wing geometry is broadly defined by the aspect ratio and the radii of the wing's moment of inertia, which can be optimised to obtain the highest possible lift at a given Reynolds number. However, the shape of the leading edge can also affect the LEV and the tip vortex structure. A straight leading edge and a sharp wingtip can affect the spanwise vorticity flux responsible for a stable LEV, thereby affecting the lift and drag. To investigate this in the current study, the wing shape is initially approximated by the Beta function with a straight leading edge and is varied systematically by increasing the leading-edge curvature. The lift and power economy are observed to be enhanced with the leading-edge curvature. The reasons behind the lift enhancement are further investigated by analysing the LEV structures over the wings of various leading-edge curvatures. The curved leading edge is observed to enhance lift at both low as well as high Reynolds numbers relevant to insects.