Blade loading performance of a floating wind turbine in wave basin model tests

In this paper, we propose a blade loading sensing system for model tests of floating wind turbines (FWTs) in the wave basin. The sensing system is based on Fiber Bragg Grating (FBG) sensors and a Fiber Optical Rotary Joint (FORJ). Systematical model tests are conducted for the novel SJTU-S4 FWT in the wave basin to reveal the characteristics of FWT blade loads under different environmental conditions. Results show that the developed FBG-FORJ system performs well to capture the FWT blade loads while not smearing other FWT dynamics. The FWT blade loading is determined by gravity, centrifugal force, aerodynamic loads, as well as wave and current excitations. The driving wind takes the lead in the FWT blade loads. An increased driving wind corresponds to increased blade loads in magnitude and fluctuation, as well as increased nP (n times per revolution) harmonics. The incident wave generates considerable responses at the wave frequency and introduces more loading fluctuations. The current tends to eliminate the floater inclination generated by the driving wind and subsequently mitigates the unsteady blade loading, despite the increased floater sway and roll fluctuations. This work extends the knowledge of FWT aerodynamics and helps to investigate advanced FWT control strategies.