On the hydrodynamics of ray-like swimming
Bottom, Richard Glenn, II
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Discovering the key-features of how aquatic swimmers such as stingrays propel themselves in nature can inspire the next generation of underwater vehicles with improved maneuverability and decreased noise signatures. To discover the key-features of stingrays swimming, fluid-structure interaction simulations of a self-propelled virtual stingray, modeled closely after the freshwater stingray, Potamotrygon orbignyi, are performed. The first closed-form kinematics description of the stingray's body motion was developed from three-dimensional experimental measurements of undulatory body motion of the fresh water stingray, Potamotrygon orbignyi, which is prescribed in our simulations. The self-propelled simulations produce a high-resolution view of the three-dimensional flow field and quantifiable forces created from the stingray's swimming unobtainable by other experimental means. A leading edge vortex (LEV) was discovered to be present on the pectoral disc of the stingray, which drastically affects the hydrodynamic forces and the pressure distribution on its disc. The LEV was found to stays attached to the stingray's body until its swimming cycle reverses direction at which time the vortex detaches to travels along with the stingray's swimming undulations, creating pressure differentials across the surfaces of the stingray which promotes thrust. At the time instance of highest thrust generation during its swimming cycle, three separate vortices present on the stingrays body, all of which were formed on the leading edge, are creating a pressure distribution promoting thrust. This finding can inspire new propulsive fins that generate LEV instead of mitigating separation.