Coupled analysis of floating offshore wind turbines with new mooring systems by CFD method

Abstract

This paper presents a fully coupled aero-hydro-mooring numerical model of the National Renewable Energy Laboratory's (NREL) 5 MW OC4 semi-submersible Floating Offshore Wind Turbine (FOWT). The model's accuracy was validated through comparisons with existing experimental and numerical data, utilizing OpenFOAM, a Computational Fluid Dynamics (CFD) software. The key contributions of this study include demonstrating the model's precision in predicting aerodynamic performance, motion responses, and mooring system dynamics under wind and wave conditions. Additionally, a comparative analysis is conducted between a Conventional mooring system (CMS) and a New mooring system (NMS). The results show that the NMS offers improved stability in surge and heave motions, crucial for operational effectiveness and resilience. Furthermore, the NMS demonstrates a more efficient stress distribution and also reduced tensions in the mooring lines, contributing to the long-term durability and safety of the structure. In terms of aerodynamic performance, the differences between the two mooring systems are limited due to the combined surge and pitch motion phase difference. Future research will focus on optimizing these phase differences to enhance performance and refine the cost-efficiency of the mooring system.