Recently, it has been found that aerodynamic damping has significant effects on the dynamic responses of offshore floating wind turbines in operating conditions. This study seeks to investigate the aerodynamic damping effects on an OC4 semi-submersible floating wind turbine by a series of scaled model tests. It is found that the aerodynamic damping effects are active in reducing the resonant responses of the surge and pitch motion. Furthermore, the aerodynamic damping is influenced by the incoming wind speed and the rotating blades. In addition, it is found that the aerodynamic damping suppresses the vibration of the tower. Finally, it is found that the redesigned performance-matched blades potentially have a higher fidelity in the aerodynamic damping than the geometrically similar blades.
Nowadays, floating offshore wind turbine (FOWT) technology is attracting more and more attention due to steady and strong offshore wind, less noise, less visual pollution, fewer space limitations and more economical applications in deeper water regions (Bae and Kim, 2013). Recently, it has been found that aerodynamic damping plays an important role in the FOWT system, since it can reduce some resonant responses, fatigue damage (Karimirad and Moan, 2010; Cheng et al., 2016). Nevertheless, Larsen and Hanson (2007) found that the aerodynamic damping could be negative and cause a larger motion in the FOWT when the pitch control for blades is too fast. In other word, the traditional control strategy applied to onshore wind turbines is inappropriate for the FOWTs. Therefore, more investigations on the aerodynamic damping are necessary for the FOWTs. On the other hand, since the aerodynamic damping of FOWTs could be affected by the aerodynamic characteristics of blades, and motions of the floating platform and even the structural vibration, aerodynamic damping is a nonlinear and coupled issue actually. Therefore, it could be the one of effective methods to conduct a relatively reliable model experiment to investigate the aerodynamic damping of the FOWTs.