Abstract
Fast swimming of dolphins has fascinated biologists and engineers for decades. Power output performance of dolphins is still a controversy topic till now, which is well known as the "Gray's Paradox," because it yet remains as a challenging problem of accurately estimating fluid drag / thrust acting on the realistic body of dolphins by quantifying its three-dimensional geometry. Here we reconstructed a realistic dolphin model by measuring an at-scale replica of a dolphin using a three-dimensional scanner. We then built a computationbal fluid dynamic (CFD) model and conducted a CFD analysis to compute velocities and pressures and hence calculate hydrodynamic drag forces of the dolphin. Our results demonstrated that the pressure drag component of the dolphin model was much larger than that of a simplified hyrodynamic model when the swimming speed reached maximum. Furthermore the estimated mass-specific power of the dolphin (84.0 W/kg) also showed larger value than that of the simplified model (51.3 W/kg). These results suggest that accurate three-dimensional geometry may play an important role in influencing hydrodynamics and should be considered in analysis of dolphin fast-swimming.
