Inverted hydrofoil energy harvesting from flow-induced pitching

Ocean energy (current/wave energy) is a promising type of sustainable energy with mature harvesting technologies, and its efficient exploitation relies on systematic fluid dynamics research. This study numerically investigates energy harvesting from flow-induced pitching of an inverted hydrofoil for a non-dimensional reduced velocity U_r = 25 – 47 and damping ratio ζ = 0 – 0.325, focusing on the foil oscillation amplitude, hydrodynamic power output, energy transfer, and vortex dynamics. The finite-volume method is employed to solve the Navier–Stokes equations and the incompressible continuity equation. The system achieves a global maximum efficiency of 16% at U_r = 37 and ζ = 0.130. High efficiency is achieved when three conditions are met: the system maintains only a positive hysteresis region, maximum energy delivery occurs near the foil mean position, and the foil exhibits symmetric pitching in the spatial domain. This understanding provides valuable insights for the optimal design of flow-induced marine energy harvesting devices in coastal and offshore low-speed flow environments.