Effect of humpback whale-like leading-edge protuberances on the low reynolds number airfoil aerodynamics

Abstract

An experimental investigation of airfoil aerodynamics control at a low Reynolds number of 5 × 104 was conducted within the attack angle α of 0–90° using a leading-edge protuberance technique. The essence of the technique is to manipulate flow around the airfoil through the effect of a humpback whale-like leading edge. Whereas the mean lift force, drag force, and lift-to-drag ratio were measured using a 3-component force balance, the flow was mainly documented using a particle image velocimetry (PIV). The sinusoidal protuberances effectively suppressed the airfoil stall, although the corresponding aerodynamic performances were impaired to some extent. Meanwhile, the control significantly improved the airfoil aerodynamics in the post-stall a region, i.e., 16°< α <70°, leading to a maximum 25.0 and 39.2% increase in lift coefficient and lift-to-drag ratio, respectively, and maximum 20.0% decrease in drag coefficient. The flow physics behind the observations were discussed.