Quantitative assessment on fatigue damage induced by wake effect and yaw misalignment for floating offshore wind turbines

Wake interaction between floating offshore wind turbines (FOWTs) is complex and necessitates a comprehensive assessment, which is a prerequisite for the yaw misalignment control. However, existing research on the influence of the wake effect on fatigue damage still suffers from unreliable conclusions and incomplete analysis. Consequently, we aim to precisely and comprehensively evaluate the influence of the wake effect and yaw misalignment on the fatigue damage of FOWTs. Initially, FAST.Farm is employed to holistically assess the output power, motion response, and dynamic response of two semi-submersible FOWTs arranged in series under varying yaw misalignments and wind speeds. Subsequently, the fatigue damage results of tower welds are calculated and analyzed based on the damage equivalent load and the time-varying stress, respectively. Finally, extensive comparisons and summaries are made between FOWTs under different conditions on power performance, platform motions and fatigue damage. The results indicate that active yaw control of upstream wind turbines reduces their fatigue damage of tower weld while exacerbating that of downstream wind turbines. Moreover, yaw optimization control is crucial in managing the platform motion responses. •Wake effect and yaw misalignment-induced fatigue damage are quantitatively assessed.•Fatigue damage based on damage equivalent load and time-varying stress is compared.•Damage equivalent load cannot determine maximum fatigue damage point accurately.•Active yawing decreases fatigue of front wind turbines but increases that of latter one.•Wake redirection can greatly improve wind farms' output power at low wind speeds.