Study on the Effect of Mooring Form on the Dynamic Response of Floating Offshore Wind Turbine

Mooring system is a key factor affecting the dynamic response of a floating wind turbine, and it is related to the safety and efficiency of the wind turbine system. To study the effect of different mooring systems on the dynamic response of floating wind turbines, this paper took a new type reduced-draft floating foundation as the research object. Based on the feature of large reserve buoyancy, two different mooring systems, namely the catenary lines and the tension legs, were used for positioning the 5 MW floating offshore wind turbines. The turbine-buoy-mooring coupled numerical model was established. The aerodynamic load was calculated based on the blade element momentum theory, the hydrodynamic load was calculated by the potential flow theory, and the tensions in the two kinds of mooring lines were calculated by the three-dimensional finite element dynamic model. Based on this coupled numerical model, the dynamic responses of two kinds of floating wind turbines under the operating state were simulated in the time domain. By comparing the results, it shows that under the rated operating sea conditions and compared with the catenary mooring system, the mean of surge motion of the floating wind turbine with the tension leg mooring system is reduced by 0.7 m, the amplitude of heave motion is reduced by 39%, and the mean and amplitude of pitch motion are reduced significantly. The floating wind turbine with the tension leg mooring system has better motion performance, but its mean and amplitude of the tension in the mooring lines are larger, and the variation amplitude of the output power and the tip deformation of the wind turbine are also more significant. Therefore, for the new floating foundation proposed in this work, the wind turbine with tension legs has better motion performance, but its mooring safety and power generation efficiency are not as good as the turbine with catenary mooring lines.