In recent years, wind turbine blades have been progressively designed toward larger size and higher flexibility to improve wind energy utilization efficiency. The slender, flexible blades exhibit significantly enhanced geometric nonlinearity, thereby inducing complex dynamic phenomena. Based on Hamilton’s principle, this paper derives the nonlinear dynamic governing equations of wind turbine blades under the parked condition by considering third-order nonlinear truncation. The equations are discretized via the Galerkin method with retention of the first four modal orders. Furthermore, the nonlinear dynamic characteristics of a 15 MW wind turbine blade under this parked condition are investigated by varying wind speeds and excitation frequencies. The results demonstrate that near the system’s natural frequency, unstable amplitude responses emerge, and the specific dynamic behavior depends on initial conditions. Variations in initial conditions may drive the system to transition from low-dimensional quasi-periodic motion to high-dimensional quasi-periodic motion. Wind speed influences the unstable solution intervals by modulating geometric nonlinearity effects and alters the structural nonlinear stiffness, which disrupts internal resonance conditions and consequently affects inter-modal energy transfer and energy decay rate.
Du et al. (Mon,) studied this question.