NUMERICAL STUDY ON OSCILLATING HYDROFOILS FOR ENERGY EXTRACTION

The global pursuit of clean and renewable energy has driven interest in unconventional technologies capable of operating efficiently in variable aquatic environments. Among these, flapping hydrofoils have emerged as a bioinspired solution for sustainable hydrokinetic energy harvesting. Using flapping hydrofoils is a promising approach to capturing hydrokinetic energy from river and tidal flows. Unlike traditional rotational mechanisms, flapping hydrokinetic devices offer several advantages, including simpler foil geometries, reduced structural demands, improved hydrodynamic performance, suitability for shallow waters, and lower impacts on aquatic ecosystems. While previous numerical studies have mainly focused on hydrofoils with fully prescribed motions, this study investigates the energy harvesting performance of an oscillating hydrofoil using a semi-passive model strategy. The pitching motion is prescribed while the heaving response is driven purely by unsteady hydrodynamic forces. A fully prescribed configuration is also simulated under matching flow and motion conditions to enable direct performance comparison. Simulations are performed using a 2-D unsteady Reynolds-Averaged Navier–Stokes (URANS) framework implemented via overset mesh around a NACA0012 hydrofoil in ANSYS Fluent. The numerical model is set at a Reynolds number of 3.6×105, representative of practical deployment in riverine environments.