Investigation of Six-Degree-of-Freedom Motion Response Characteristics of a 22 MW Semi-Submersible Floating Wind Turbine Platform

Abstract A fully coupled aero–hydro–servo–elastic model of a 22 MW semi-submersible floating wind turbine is established using OpenFAST. After validating the hydrodynamic module via still-water and free-decay simulations, we systematically investigate the sensitivity of the platform’s six-degree-of-freedom motions (6-DOF) to uniform wind velocities between 5 and 23 m/s. The results reveal that surge and pitch motions are dominated by aerodynamic loads, reaching peak values around 11 m/s (19.1 m and 5.19°, respectively) and subsequently decreasing beyond the rated wind speed due to pitch control reducing rotor thrust. In contrast, heave, sway, and yaw motions are primarily governed by wave excitation and mooring forces and are insensitive to changes in wind speed. These findings provide a useful basis for evaluating the wind-speed adaptability and motion-control strategies of ultra-large-capacity semi-submersible floating wind turbines.