Aero-Elastic-Control-Floater-Mooring Coupled Dynamic Analysis of Floating Offshore Wind Turbines

In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of a FOWT (floating offshore wind turbine) in time domain including aero-loading, blade-rotor dynamics and control, tower elastic responses, mooring dynamics, and platform motions so that their dynamic coupling effects can fully be assessed. The rotor-floater coupled analysis is compared with the uncoupled analysis to identify their coupling effects to the global performance of the whole system. In this regard, Hywind spar design with 5MW turbine is selected as an example. In case of the spar-type floater, it is seen that the maximum offsets and mooring tensions of the coupled analyses are smaller than those of uncoupled analyses. It is also seen that the maximum accelerations at the tower are significantly increased due to the coupling between tower elastic modes and hull 6DOF motions, which will in turn greatly affect the corresponding inertial loading on nacelle and blades. The developed technology and numerical tool are readily applicable to the design of any new offshore floating wind farms in any combinations of irregular waves, dynamic winds, and steady currents.