Experimental Investigation on Vortex Evolution and Lift Variation with Varying Leading-Edge Geometries

The evolution of leading-edge vortex (LEV) and corresponding lift variation of a pitching and plunging plate with varying leading-edge geometries are studied in a water tunnel experimentally. Different leading-edge wedges are used in the present research to investigate the leading-edge geometry effects. The NACA 0012 airfoil is also included as comparison. The upslope in the leading edge is found to be the key to influence the flow separation and development of LEV. Both the movement of separation location and negative pressure limitation effect on the growing LEV result in the suppression of the LEV development. The separation point moves with plate motion, which significantly delays the formation time of LEV. These suppression effect becomes weak with the increase of effective angle of attack. Under the effect of upslope, the effective inflow condition still governs the growth rate of LEV circulation for all tested leading-edge shapes. The change in LEV development leads to different aerodynamic force characteristics. The leading-edge geometry which is beneficial for the LEV development brings higher overall lift. With the increase of maximum effective angle of attack, the leading-edge curvature extends the LEV duration time and helps to increase the averaged and maximum lift.