Motion and elastic response of wind-tracing floating offshore wind turbines

Abstract

A multi-unit floating offshore wind turbine concept, the wind-tracing floating offshore wind turbine, is introduced. In this concept, the floating structure is a triangular platform that hosts three 5 MW wind turbines and is moored to the seabed with a turret-bearing mooring system. This mooring system allows the structure to rotate about the turret such that the total yaw moment by the environmental load on the turret is minimized. In this study, the optimum properties of the mooring lines and the location of the turret are determined. To identify the preferred location of the turret, the responses of the structure to combined co-directional and misaligned wind and wave loads are computed. The motions of the structure are obtained with a frequency-domain numerical model integrated with structural finite-element method for hydroelastic and aeroelastic analyses. The hydrodynamic and aerodynamic loads are obtained by wave diffraction theory and steady blade element momentum method, respectively. Finally, with the optimum configuration of the mooring system, the motion and aero- and hydroelastic responses of the fully flexible wind-tracing floating offshore wind turbines to combined waves and wind loads are determined and discussed.