Coupled aero-hydro-servo-mooring dynamic responses of a semi-submersible floating offshore wind turbine subjected to wind, wave and current loading

Abstract

To investigate the dynamic response of a semi-submersible floating offshore wind turbine (FOWT) under combined wind, wave, and current conditions, an integrated multi-physics time-domain dynamic model was developed based on blade element momentum (BEM) theory and potential flow theory. This study investigates aerodynamic performance, platform motions, and mooring tension characteristics under different environmental conditions, revealing the influence mechanisms of these factors on the FOWT system. Research indicates that wave loads dominate dynamic oscillations. The heave response increases to 4.35 times its original value near resonance with the natural period, while exhibiting weak coupling with aerodynamic performance. Increasing wave height induces nonlinear growth in platform responses, with peak surge displacement doubling and pitch motion increasing by 53.6 %. This intensification of second-order slow-drift excitation further raises rotor thrust fluctuations by 28.2 %. Wind loads primarily determine steady-state platform attitudes and power production, with rated wind speed producing the largest mean offsets and stronger aerodynamic load fluctuations. Ocean currents primarily induce static equilibrium shifts, increasing the mean platform offset by 12.9 %. However, the influence of current velocity on dynamic response amplitudes and aerodynamic performance is less than 1 %.