Aerodynamic analysis of a downwind offshore floating wind turbine with rotor uptilt angles in platform pitching motion

Abstract

In this study, the effect of the rotor uptilt angle on the aerodynamic performance of a downwind floating wind turbine (FWT) is investigated using the free vortex wake (FVW) method. The Weissinger-L blade lifting model and a three-step, third-order predictor-corrector difference approximation of wake solution are applied in the FVW model. To consider the platform pitching angle and angular velocity, the blade inflow conditions and the positions of the first three nodes of vortex filaments are modified in the implemented model. The full-scale FWT simulation results, focusing on platform pitching motion, are validated by comparing them with results obtained using other established numerical methods, ensuring the accuracy and reliability of the presented model. Furthermore, the simulation of the wake field is also validated by comparison between calculation and experiment. In this setting, the comparison of the aerodynamic performance between upwind and downwind FWTs shows that the downwind FWT with a rotor uptilt angle has slightly higher power and thrust. The results indicate that the rotor uptilt angle has a significant effect on blade aerodynamic loads, with the highest impact observed at maximum pitching velocity and angle. In this context, at the position with maximum pitching velocity, a larger rotor uptilt angle results in a larger angle of attack and increased aerodynamic load, while at the maximum pitching angle position, a larger rotor uptilt angle leads to a smaller angle of attack and decreased aerodynamic load.