Parametric Sensitivity Analysis of Mooring Chains of a Floating Offshore Wind Turbine in Shallow Water

Floating offshore wind turbines (FOWTs) are severely restricted in numerous sea areas due to challenges from the strong nonlinear characteristics of mooring chains in shallow water (less than 50 m). Therefore, this paper introduces a design method of mooring chains of a FOWT at a water depth of 44 m and carries out a parametric sensitivity analysis on length, nominal diameter, and clump weights of mooring chains. The results of the study found that compared with the mooring chains in deep water, the mooring chains in shallow water show obvious nonlinear characteristics in mooring tension, the lying section of the mooring chain on the seabed, and the mooring chain spatial angle, which brings great risk to the safe operation of FOWTs. The change in the nominal diameter of the mooring chain has a certain impact on the dynamic characteristics of a FOWT, but it is not as significant as that from the change in the length of the mooring chain. In addition, a mooring chain in shallow water is prone to the slack–taut phenomenon; thus, this paper puts forward an optimization investigation using clump weights at the suspension section of the mooring chain, which improved the performance of the mooring chain significantly.