Shark Skin-Inspired Surface Features to Enhance the Hydrodynamic Performance of Flapping Fin Propulsion

Power constraints are a major limiting factor in uncrewed underwater vehicle (UUV) performance. Increases in UUV efficiency and endurance can benefit efforts in remote environmental monitoring, ocean exploration, and underwater surveillance. We designed and tested a robotic tandem fin propulsion system by varying the fins’ spacing, geometry, and phase offset, combined with shark skin-inspired surface structures for enhanced hydrodynamic benefits. Surface structures were modeled from the interlocking, tooth-like denticles of shark skin, which are known to alter vortex interactions within the boundary layer to reduce drag and increase lift. We constructed a robotic experimental setup that can create flapping motions inspired by finned aquatic animals to test the combined effects of denticles on the drag, lift, and thrust of single and tandem 3D flapping fins with various motion profiles. By measuring the forces and torques on fins with and without denticles, we determined how various denticle configurations (e.g., denticle size, placement, and quantity) alter the lift and thrust production of both leading and trailing fins. By drawing inspiration from multiple model organisms, such as sharks, polypteruses, and flying fish, we demonstrate how influences from multiple model organisms can be combined to create technologies for more efficient and maneuverable UUVs.