Integrated numerical investigation of a 15 MW semi-submersible wind turbine at moderate water depth

Abstract

Numerical simulations of dynamic responses of 15 MW offshore floating wind turbine are performed by an integrated FAST-OrcaFlex coupling model. An integrated model is established for an IEA 15 MW reference wind turbine (RWT) mounted over a semi-submersible floating platform, where the mooring line system and dynamic cable are designed at a moderate water depth h = 50m. The dynamic responses of 15 MW FOWT, mooring line system and dynamic cable are discussed, and the characteristics of load, displacement, mooring tension and bending curvature of dynamic cable at different IEC design load cases are investigated by the integrated time-domain simulations. The results indicate that the mean response of 15 MW FOWT is found to be mainly depended by the wind load, while the standard deviation of response is mainly influenced by the wave load. The mooring line system remains within the safe design range during the extreme environmental conditions. Moreover, the dynamic response of dynamic cable is influenced by the combined effects of the floating platform and ocean environmental factors. Large curvatures are observed in the buoyancy and boundary-layer sections, and high tensions are observed at the hang-off point, decline section and anchor point.