CFD analysis of the influence of structural parameters on the hydrodynamic characteristics of oscillating swept hydrofoils

Abstract

The structure of the hydrofoil plays a crucial role in determining its hydrodynamic coefficients. Drawing inspiration from the swept-back morphology of fish caudal fins, this study developed two novel oscillating hydrofoil configurations: a leading-edge swept-back design and a trailing-edge swept-forward design. The corresponding mathematical formulations and parameter definitions are provided. Utilizing computational fluid dynamics techniques, the study investigates the influence of sweep angle and pitch axis position on the hydrodynamic performance of swept hydrofoils. The findings demonstrate that increasing the sweep angle can enhance the lift-to-drag ratio of the hydrofoil but also leads to an increase in the pitching moment power coefficient, with a more substantial impact on the latter. The increased negative work resulting from larger pitching moments further reduces the average power output. With the pitch axis oriented toward the trailing edge, the moment coefficients initially decline and subsequently increase. Accordingly, the average power output also exhibits a trend of first increasing and then decreasing. Therefore, the pitch axis should be positioned near the mid-chord of the hydrofoil. A larger sweep angle is preferable in complex flow environments, while a smaller sweep angle is more suitable when higher energy harvesting efficiency is desired.