Hydrodynamics of River Stingrays and Applications to Underwater Vehicles

While pelagic movement for underwater vehicles is widely studied, there has been limited studies of benthic stingrays swimming close to the ground. With inspiration from the ocellate river stingray (Potamotrygon motoro), this research explores the hydrodynamics of benthic animals when locomotion is close to the ground. A 3-D stingray model replicated the dorsoventral body structure of the ocellate river stingray and resembled a hydrofoil. The experimental setup consisted of two water flume flow speeds, 17 cm/s and 26 cm/s, corresponding to laminar and turbulent Reynolds numbers, respectively, to replicate the stingray pectoral fin flow speed. Force and flow experiments recorded the hydrodynamic effects on the stingray model at various heights from the substrate. Force results stated a significantly high lift-drag ratio when the model was closest to the substrate and rapidly decreased with height above the ground. Flow analysis around the model was observed using UV fluorescent dye and measured using particle image velocimetry (PIV). A specific focus was on the head morphology hydrodynamics to determine the possible contribution to negative lift created from force measurements. Additionally, computational fluid dynamics compared the hydrodynamic relationships from the experimental results. The digital stingray model was placed in a recreated water flume to replicate the experiments from the laboratory. We will discuss the application potential of these results related to the locomotion of benthic stingrays and underwater vehicles that swim close to the ground.