Co-Generation and Platform Motion Control Potential of Oscillating Hydrofoil Turbines Under Floating Offshore Wind Turbine Platforms

Due to increasing energy demand and the global shift toward greener energy sources, wind energy is expected to supply a significant share of the world's power. Floating offshore wind turbines (FOWTs) offer a promising way to harness stronger deep‑water winds. Although the aerodynamic performance of offshore turbines has been extensively researched, the motions of the floating platform remain a continuing challenge. Specifically, pitching motions can reduce turbine efficiency, and undamped motions induced by waves may damage the structure and mooring lines, potentially causing system failure under extreme conditions. One method for motion control involves using oscillating hydrofoil turbines mounted beneath the FOWT platform. These hydrofoils can both damp platform motions and co‑generate energy from water currents. The current study addresses the one‑way coupled effects of attaching such hydrofoils to a FOWT. The FOWT is modeled using OpenFAST, with resulting platform kinematics provided as input to our in‑house 2D unsteady boundary‑element-method solver. That approach enables superposition of platform and hydrofoil kinematics. Based on hydrodynamic forces and platform motions, it is possible to analyze power transfer between the hydrofoils and the FOWT. This analysis indicates whether motions are effectively damped or whether added hydrofoils exacerbate motion. Our main goal is to identify the parameter space that enables both high co‑generation of power and platform stability.