A medium-fidelity wake model of floating wind turbines considering the double Gaussian virtual force

Wake models are the foundation for the study of floating offshore wind turbines (FOWTs). Existing research mainly concentrates on the high fidelity and low fidelity wake models. This paper aims to develop a wake model with the medium fidelity. First, a simplified dynamic motion equation of FOWTs in two degree-of-freedoms considering the pitch and surge is established and then integrated into the conventional WFSim framework. More importantly, the concept of virtual force is proposed for the first time to address the flow distribution and energy dissipation issues caused by the three-dimensional effects and fluid viscosity, and the double Gaussian profile of the virtual force is further developed. Finally, the simulation results of the improved WFSim model are compared with those of the full-scale three-dimensional simulation and the OpenFAST. The results demonstrate that the developed medium-fidelity model has well accuracy in the motion responses, aerodynamic force, power, and wake fields under various conditions including the wind-only, wave-only, and combined wind and wave, from the engineering perspective. The model constructed in this paper provides a vital tool for the research of FOWTs and the planning and operation of floating wind farms.