Effects of Platform Motions on Dynamic Responses in a Floating Offshore Wind Turbine Blade

ABSTRACT: Floating offshore wind turbines (FOWTs) offer great potential for harnessing deep-sea wind energy. This study examines the effects of six-degree-of-freedom (6-DOF) platform motions on the dynamic structural responses of a FOWT blade by comparing its performance with a fixed-bottom system. Integrated aero-hydro-servo-elastic simulations for a 5-MW spar-type FOWT were conducted under various design load cases. Results indicate that the floating tower’s first-order natural frequency was about 29% higher than that of the fixed-bottom tower. Platform motions markedly influenced blade flapwise and torsional responses, with the effect intensifying under larger waves. For instance, as the significant wave height increased from 1.70 m to 9.90 m, the differences in peak response between the floating and fixed-bottom systems grew from 0.104 m to 0.363 m for blade-tip flapwise deflection, from 528.1 kN·m to 1817.4 kN·m for the root flapwise bending moment, and from 5.02 kN·m to 18.73 kN·m for the root torsional moment. In contrast, blade edgewise responses showed negligible changes, with peak deflection differences below 0.05 m. Blade loads were more sensitive to wave conditions, while platform motion magnitudes were more affected by wind. These findings offer insights into the load characteristics and structural design of FOWT blades.