How bumps on whale flippers delay stall: An aerodynamic model

Wind tunnel experiments have shown that bumps on the leading edge of model humpback whale flippers cause them to stall (i.e., lose lift dramatically) more gradually and at a higher angle of attack. Here we develop an aerodynamic model which explains the observed increase in stall angle. The model predicts that as the amplitude of the bumps is increased, the lift curve flattens out, leading to potentially desirable control properties. We find that stall delay is insensitive to the wavelength of the bumps, in accordance with experimental observations.