Dynamics and propulsive efficiency of bio-inspired undulatory marine locomotion

Computational fluid dynamics (CFD) was used to investigate the fluid mechanics for undulatory stingray locomotion. This method of undulatory propulsion can be utilized to generate non-turbulent thrust with minimal disturbance to the immediate environment, ideal for exploratory vehicles for underwater environments. Undulatory locomotion was modeled as a two-dimensional fin in free flow with a deforming non-slip boundary to represent a propagating sinusoidal wave with a linearly increasing amplitude, constant frequency, wavelength and flow velocity. In the presented computational study, we varied the amplitude, wavelength, frequency, and flow velocity parametrically and examined the effect on thrust, lift, and pitching moment. Average net thrust was found to increase with wavelength and frequency, whereas for this two-dimensional case amplitude showed negligible effects. For the parametric cases, a theoretical efficiency for forward propulsion was then calculated for a continuous fin. The amplitude was found to increase the input power required for actuation, but decreased output power for forward thrust. Variation of the other parameters showed that the output power depends nearly linearly on the input power, regardless of the particular kinematics or swimming speed.