Meeting Abstract
During lunge feeding by rorquals (e.g., blue, humpback, minke whales), the lower jaw is depressed as the throat pouch is inflated to engulf a large mass of prey-laden water. The resulting increase of mass of the whale and drag from inflation of the pouch could result in down-pitching torque of the head. A previous model for a rorqual estimated that an opposite rotation could produce lift generated from the pectoral flippers to help offset the downward pitch and stabilize the body in trim. Videos from suction-cup tags mounted on the backs of feeding rorquals showed that not only are the flippers deployed with a positive angle of attack for lift generation, but the upper jaw is elevated with a positive angle of attack. The planform of the upper jaw has a modified acute triangular shape that is similar to a highly swept delta wing. Delta wings are capable of generating lift without stalling at higher angles of attack than unswept wings that typically stall at 11 deg. Data from published accounts and videos of lunge feeding rorquals indicate that the angle of attack for rorquals varies from 11.8 to 31.8 deg. Based on morphological data from aerial drones and kinematic data from tags of known whales, a computational analysis based on a delta wing of lift production was performed. The maximum lift from the upper jaw was calculated to be 2136, 8015, and 18562 N for minke, humpback, and blue whales, respectively. The lift from the upper jaw in concert with the flippers could stabilize the body during lunge feeding.
