Numerical study on the impact of structural flexibility and platform motions on the dynamic behaviors and wake characteristics of floating offshore wind turbine

Structural flexibility and six degrees of freedom (6-DOF) platform motions influence the dynamic behaviors and wake characteristics of the floating offshore wind turbine (FOWT). However, current quantitative studies on these effects remain insufficiently comprehensive. In this study, fluid-structure interaction simulations are conducted to investigate the impact of structural flexibility and 6-DOF motions on FOWT using the coupled computational fluid dynamics software SOWFA and turbine simulation tool OpenFAST. Various cases are analyzed, including rigid and flexible structures, as well as configurations with different DOF activated. The dynamic behaviors and wake characteristics, including rotor power, platform motions, wake velocity deficit, and vortex structures, are comprehensively compared. The results indicate that structural flexibility has a stronger impact on power reduction than 6-DOF motions, and blade flexibility has a greater overall impact compared to tower flexibility. Specifically, blade flexibility leads to a power decrease in 166.31 kW, while tower flexibility leads to 17.62 kW. Among the 6-DOF motions, pitch causes the largest power decrease in 96.06 kW. Moreover, coupling effects between different 6-DOF motions are identified, with roll motion inducing low-frequency components in sway motion, emphasizing the necessity of considering such interactions for accurate motion predictions.