Effects of leading edge protuberances on the aerodynamic performance of 2D cambered airfoil

Abstract

The pressure and lift coefficients were measured for airfoils with leading edge protuberances in a subsonic wind tunnel and compared with the performance of a baseline NACA 4415 airfoil with a straight leading edge. These protuberances of 2D airfoil mimic the leading edge configuration of the flippers of a humpback whale. Wavelengths were varied from 25% to 50% of the chord length whilst amplitude was varied from 5% to 12% of the chord length of the baseline. Surface flow visualisation using kaolin was also performed to further analyze the flow patterns and surface swirls and vortices were observed. The presence of protuberances enhanced the stall characteristics of the baseline and low amplitude protuberances exhibited the maximum lift coefficient. However, at low angles of attack, the performance of the modified airfoils is similar to that of the baseline.