Impact of Wind-Wave Misalignment and Wave Directionality on Fatigue Damage of Floating Wind Turbines

Ongoing climate change and worldwide policies are driving a shift towards low-carbon electricity generation. Within this context, offshore wind energy plays a pivotal role. To extend the use of wind turbines in deep waters, floating systems have recently been proposed and tested in pre-commercial installations. However, the harsh marine environment poses significant structural challenges, especially for long-term reliability. Appropriate fatigue design is therefore crucial to ensure safety and to avoid costly emergency maintenance operations. Significant uncertainty remains in modeling the wind and wave climate and their impact on the fatigue life of floating wind turbines, particularly regarding wave directional spreading and wind–wave misalignment. Hence, the focus of this work is to evaluate their influence on the fatigue damage at the interface between tower and transition piece for the IEA 15 MW reference turbine coupled with the VolturnUS semisubmersible platform. Results show that the wind-wave misalignment has a significant impact on fatigue damage, because of the different behavior of the platform for several wave directions and its interaction with the wind field. Moreover, when considering wave directional spreading, preliminary results indicate that the fatigue damage associated to the mean wave direction decreases, while increasing across the full range of investigated directions.