Numerical and experimental study of the dynamic response of a wind-wave combined energy platform under WEC motion constraints

The motion response of a wind–wave-combined energy platform with and without a wave energy converter (WEC) was analyzed using numerical simulations and wave tank experiments. The effects of the WEC power take-off (PTO) and WEC motion constraints on the motion response of the platform were also analyzed. The analyzed model consisted of cylindrical WECs attached to a spar-shaped floating offshore wind turbine (FOWT) from front to back. Numerical analysis was performed using a potential-flow-based hydrodynamic program (ANSYS AQWA) based on the boundary element method to perform time domain analysis. Nonlinear Froude–Krylov forces and hydrostatic forces were considered to improve the accuracy of the numerical results. The dynamic interactions between the FOWT and the mooring lines were considered. The numerical results showed good agreement with the experimental data. The pitch and heave of the combined platform were reduced significantly by the motion of the WEC attached to the FOWT. In particular, the rotational motion of the WEC had the greatest impact on the motion reduction of the platform. This effect helped reduce the mooring tension. On the other hand, the pitch response of the platform increased slightly when the WEC was fixed to the platform (no motion) or when a large PTO coefficient was applied.