Watts, P.*; Fish, F.: Fluid Dynamic Role of Tubercles on Humpback Whale Flippers

Tubercles are leading edge protrusions on the flippers of humpback whales (Megaptera novaeangliae). Humpback whales are the only baleen whales that capture prey through routine tight maneuvers. We investigated the fluid dynamic benefits of tubercles with regard to force production by the flippers. Fluid dynamic simulations were carried out with inviscid, panel method, computer simulations applied to steady, three-dimensional flow about an airfoil. At a modest angle of attack of 10 degrees, the tubercles enhance lift by 5% and reduce drag by 10%, respectively. The additional lift is derived in part from low pressure regions between tubercles. Drag is reduced through several mechanisms, although the dominant one is lowered induced drag due to compartmentalization of the low pressure regions over the airfoil. The result is an increase in both the relative and absolute performance of humpback whale flippers as control devices during tight maneuvers. In modifying the flow over the flipper, the tubercles can also extend the useful performance envelope of the flipper. This work provides the first dynamical evidence that tubercles could indeed be functional adaptations that enhance prey capture for humpback whales.