Large-amplitude rotation of floating offshore wind turbines: A comprehensive review of causes, consequences, and solutions

Floating offshore wind turbines (FOWTs) have emerged as a promising option for harnessing offshore wind resources, benefiting from better wind conditions in offshore areas, minimal impact on nearby coastal installations, and the ability to accommodate larger turbine sizes. Field measurements and physical model tests have demonstrated the occurrence of large-amplitude rotation in FOWTs, posing potential threats to structural integrity and causing fluctuations in electricity generation. Some studies have addressed these issues, but targeted and systematic research is noticeably lacking. This review aims to comprehensively identify and analyse the root causes of large-amplitude rotation in FOWTs, categorising them into various aspects such as hydrostatics, hydrodynamics, and aerodynamic loads, etc. The effects of nonlinear wave loads, low-frequency rotation, and negative aerodynamic damping are discussed in detail. Existing solutions proposed to mitigate large-amplitude rotation, including blade pitch control, tuned mass dampers, active ballast, and tuned liquid dampers, are summarised and evaluated. Nevertheless, most solutions to date have been adapted from fixed wind turbines. Accordingly, more specific and efficient measures must be proposed based on a more adequate understanding of the behaviour and causes of large-amplitude rotation.