Dynamic response analysis and blade stiffness sensitivity study of large floating offshore wind turbine with coupling effect

The rise in offshore wind energy deployment has driven the design of larger blades, creating a trade-off between structural optimization and economic feasibility. To investigate the interaction between structural and sub-component responses in offshore floating wind turbine blades, a multi-body dynamics method, geometrically exact beam theory, and coupled blade element momentum theory were employed. A dynamic model was developed to assess the dynamic response of the 15 MW floating wind turbine under steady wind conditions. The geometrically exact beam theory accounts for the complete 6×6 stiffness matrix and incorporates sensitivity analysis factors to quantify the influence of all stiffness components on the response of each sub-component. The results indicate that, for the principal diagonal stiffness, torsional stiffness has a significant impact on the response, with a sensitivity factor of −100 concerning the blade tip’s twist angle fluctuation. For the coupling stiffness, the torsion-bending coupling stiffness induces considerable divergence in the response, with its sensitivity factor reaching −657.22 for twist angle fluctuations. The six-degree-of-freedom platform motion intensifies the coupling of the torsion-bending coupling stiffness with blade dynamics, leading to amplified response fluctuations and vibration divergence.