Meeting Abstract
Estimation of force generated by swimming dolphins has long been debated. The problem has been that early indirect estimates of force production for dolphins resulted in low values that could not be validated. Bubble Digital Particle Image Velocimetry (DPIV) was used to measure the hydrodynamic force production for dolphins during free swimming and demonstrated high force production. To validate the Bubble PIV and reconcile force production measurements, two bottlenose dolphins (Tursiops truncatus) performing tail stands were measured with Bubble DPIV. Microbubbles were generated from a finely porous hose and compressed air source. Displacement of the bubbles in the wake of the dolphin was tracked with a high-speed video camera. Oscillations of the dolphin flukes generated strong vortices and a downward directed jet flow into the wake. Application of the Kutta-Joukowski Theorem on measured vortex circulations yielded force values up to 1183 N during a tail stand. Another video camera recorded the height of the body above the water surface. Based on position of the dolphin’s center of mass, the mass-force of the dolphin above the water surface was calculated. For the dolphin to hold its position above the water surface, the mass-force approximately balanced the vertical hydrodynamic force generated by the flukes. The results of this study demonstrated the fluke motion can be interpreted as a flapping hydrofoil that can generate high levels of sustained force roughly equal to the dolphin’s weight and validated high forces measured previously from Bubble PIV for thrust generated in free swimming.
