Abstract
Fatigue can be a design driver for floating wind turbines. Conducting coupled aeroelastic and hydrodynamic time-domain simulations for lifetime fatigue damage assessment is computationally intensive, taking up to thirty times longer than simulations for bottom-fixed turbines. This extended time-frame is typically impractical for commercial projects. To address this challenge, an environmental lumping method can significantly reduce the computational cost, by a factor of 20 in this study, at the expense of a small computational error (+13% in this case). Yet, limited research exists on lumping methods specifically for floating wind turbines. Unlike monopiles, semi-submersibles have an asymmetric shape and experience complex floater motions, making the relationship between sea state parameters (Hs, Tp) and fatigue damage more complex. Therefore, conclusions drawn from previous studies on lumping methods for monopiles may not be directly applicable to floating substructures. This study seeks to establish a foundation for future research in this emerging field. Among the considered lumping methods, a frequency-domain load estimation approach is identified as the most suitable for floating wind turbines.