Aerodynamic damping of a semi-submersible floating wind turbine: An analytical, numerical and experimental study

Abstract

Aerodynamic damping of floating wind turbines (FWTs) plays a dominant role in suppressing the vibration of the tower and blades and the platform motions. Although much effort has been paid to investigating the aerodynamic damping of FWTs, their characteristics and influential factors have not been studied thoroughly. In the present study, the aerodynamic damping of a semi-submersible FWT is investigated by a frequency-domain analytical method and a fully coupled decay-based time-domain method, which are validated against the wave basin model tests. Effects of controller dynamics are discussed, and then the dynamic characteristics of aerodynamic damping in surge and pitch motion are addressed. It is found that the proposed analytical method can predict the aerodynamic damping with enough accuracy and extremely high efficiency compared to the time-domain numerical method. The effects of controller dynamics should be considered in the over-rated wind speed region, especially pitch motion. Controller gains can significantly affect the aerodynamic damping in pitch motion in the over-rated wind speed region. In contrast, the initial offset and wind turbulence may not be the main influential factors. The outcomes of the present study can provide insight into the aerodynamic damping and the controller design of FWTs.