Dynamic Analysis of Shared Moorings in Different Wind Farm Layouts

ABSTRACT: The effects of shared mooring in offshore wind farms are investigated through numerical simulations in the present study. Different farm layouts are modelled and tested in SIMA coupled dynamic analysis software with three and four floaters. The wind turbine and the platform are based on the OC3 project from NREL: a 5-MW wind turbine and a spar floater with a 120-m draft. The water depth is 320 m, and the environmental loads are defined for an average operational condition. Firstly, the static results of the mooring line tension at the fairleads and anchors from the numerical model are compared with the values from the open-source MoorPy code. Then, domain simulations are conducted for three hours, and the dynamic behaviour of the floaters is analysed with a focus on surge and pitch motions. In addition, the dynamic stiffness effects of the polyester in the shared mooring line are considered in the SIMA simulations. The mooring line tensions are analysed, determining the global maximum tension across all systems. Results show that designs with two windward legs have significantly lower anchor mooring line tensions than those with a single windward leg, with no relevant variation in platform surge and pitch. Thus, the former systems are preferable for further investigation.