FISH, Frank/E; NICASTRO, Anthony/J; West Chester Univ., Pennsylvania; West Chester Univ. , Pennsylvania: Dynamics of the aerial maneuvers of spinner dolphins

The spinner dolphin (Stenella longirostris(/i>) performs spectacular leaps from the water while rotating around its longitudinal axis up to seven times. Although twisting of the body while airborne has been proposed as the mechanism to produce the spin, the morphology of the dolphin and basic physics precludes the spinning maneuver. A mathematical, physics-based model was developed to determine the causal mechanisms for the spinning maneuver. The model demonstrated that the angular momentum to induce the spin was generated underwater, prior to the leap. Underwater rotation would be initiated by canting the flippers at an angle to the direction of travel. The lateral drag on the flukes, flippers, and dorsal fin with their high moment of inertia restrict high rotation rates, when the dolphin is submerged. As the dolphin leaps clear of the water, the effective drag is reduced as is the moment of inertia. The rotation rate in the aerial phase increases by 2.85 times due to conservation of angular momentum as calculated from the model. Data collected from video of spinner dolphins showed a rotation rate increase of 2.65. Although there is no definitive reason for performing aerial spins, the model indicates that the high rotation rates and orientation of the dolphin�s body during re-entry into the water could dislodge hydrodynamically-parasitic remoras.