Hydrodynamic Performance of a Manta Ray Inspired Oscillating Fin

Myliobatidae is a family of large pelagic rays including the manta ray, Manta birostris. They are extremely efficient swimmers, can cruise at high speeds and can perform turn-on-a-dime maneuvering, making these fishes excellent inspiration for an autonomous underwater vehicle. Manta rays have been studied from a biological perspective; however the hydrodynamic performance of their large-amplitude oscillatory-style pectoral fin flapping is unknown. An experimental robotic flapping fin has been developed. Three different kinematic modes that range from simple and artificial to complex and biologicallybased are tested to determine the performance benefits of different kinematic features exhibited by the manta ray. The thrust and efficiency performance are quantified. Span-wise curvature is found to improve efficiency by a factor of two. A flat mode of swimming is found to have higher efficiency for higher swimming speeds. Finally, tip lag is found to neither improve nor degrade efficiency performance. Implications for a bio-inspired artificial pectoral fin are discussed.