Aero-hydro-servo-elastic coupled modeling and dynamics analysis of a four-rotor floating offshore wind turbine

Abstract

This paper developed a simulation framework, including multi-body dynamics, aerodynamics, hydrodynamics, controller dynamics, and mooring system, for the fully coupled dynamic analysis of a four-rotor floating offshore wind turbine (FOWT). The coupled framework is constructed based on SIMPACK, MATLAB/Simulink, user defined force element, and third-party modules to be suitable for a four-rotor FOWT. Then, the coupled framework is verified by a code-to-code method. The simulations under normal operating conditions indicate that the framework is able to investigate the dynamic responses of a four-rotor FOWT. Further capability of the framework is investigated through a case study of a parked rotor situation. The results show that the effect of an upper parked rotor is generally more significant than that of a lower parked rotor. The parked rotor reduces the tower base fore-aft loads and mooring line fairlead tensions, but increases the fluctuation of the tower base side-to-side loads. Additionally, it can be concluded that the yaw control system design is necessary because the shutdown of one of four rotors significantly affects the platform yaw responses. Furthermore, the developed coupled framework can also be extended to model bottom-fixed offshore and onshore wind turbines with different numbers of rotors.