Effect of Nacelle Motions on Rotor Performance and Drivetrain Dynamics in Floating Offshore Wind Turbines Using Fully Coupled Simulations

This study investigates the effect of nacelle motions on the rotor performance and drivetrain dynamics of floating offshore wind turbines (FOWTs) through fully coupled aero-hydro-elastic-servo-mooring simulations. Using the National Renewable Energy Laboratory 5 MW monopile-supported offshore wind turbine and the OC4 DeepCwind semisubmersible wind turbine as case studies, the research addresses the complex dynamic responses resulting from the interaction among wind, waves, and turbine structures. Detailed multi-body dynamics models of wind turbines, including drivetrain components, are created within the SIMPACK framework. Meanwhile, the mooring system is modeled using a lumped-mass method. Various operational conditions are simulated through five wind-wave load cases. Results demonstrate that nacelle motions significantly influence rotor speed, thrust, torque, and power output, as well as the dynamic loads on drivetrain components. These findings highlight the need for advanced simulation techniques for the design and optimization of FOWTs to ensure reliable performance and longevity.