Analysis of Hydrodynamic Loading on Shark Species to Inform Design of Low Drag Satellite Telemetry Tags

Abstract Sharks are pivotal apex predators in marine ecosystems and migrate up to thousands of miles throughout their lifetimes. Shark movement is studied using satellite tracking tags, which are typically attached to the dorsal fin. Tags either send a signal when the dorsal fin breaches or detach from the shark and float to surface to communicate with the satellite (Fig.1). While spatiotemporally resolved movement data is valuable to studying shark ecology and conservation, satellite tags impose hydrodynamic loading which produces a drag force on the shark, potentially influencing their behavior, leading to incorrect movement analysis. Since tags change the streamlined body shape of animals, they may influence swimming patterns, especially at high speeds since drag increases with velocity. In this study, we used existing 3D digital models of three shark species — the Great Hammerhead, Blacktip Reef, and Caribbean Reef — to assess the effects and influence future tag design. This paper explores flume testing at the OSU O.H. Hinsdale Wave Lab to improve CFD validation. A cart apparatus was glided across the flume at controlled velocities to simulate average cruising speeds of each shark species at angles of attack of 0°, 12°, and −12° degrees for neutral, rising, and diving movement patterns, respectively. We compared the output drag and lift coefficients to coefficients generated using CFD simulations in STAR-CCM+. Across the three species and angles of attack, the mean percent error was 47.3% ±34.1% standard deviation (SD) for the drag coefficient and 97.8% ±69.0% SD for the lift coefficient. Future work incorporates attaching scaled satellite tag models to shark models to compare to untagged data with the intent of informing subsequent tag designs.