Study on blade dynamic response and fatigue damage based on bi-directional fluid-structure coupling

Wind turbines operate under a variety of unsteady wind conditions, and the aerodynamic response of the blades exhibits nonlinear behavior. Study the dynamic response characteristics of wind turbine units structures under diverse wind conditions, optimize structural dynamic performance, and predict blade fatigue life, this study employs real-time bidirectional fluid-structure interaction coupled with turbulence, wind shear, gradual wind, and gust models implemented through UDF in accordance with the IEC61400-1 wind turbine standard. The dynamic responses of displacement, velocity, acceleration, stress, and strain of wind turbine components with independent intellectual property rights are analyzed under four wind conditions. Results indicate that blade tip and mid-span flapping amplitudes are significantly larger than swaying vibrations. Wind loads induce aeroelastic coupling, with blade natural frequencies approaching both flapping and swaying frequencies. The average deformation displacement and velocity are 15 mm and 0.2 mm/s, respectively. In the pendulum direction, changes follow a similar trend; however, deformation is relatively small and consistently negative, with an average displacement of 0.2 mm and an oscillation amplitude of 0.4 mm. Maximum fatigue damage occurs near the maximum blade chord length, and stress is concentrated at the connection between the blade root and the hub, leading to more pronounced damage. These findings provide a theoretical basis for wind turbine structural optimization and whether it is of great significance for extending the service life of the blades and enhancing stable turbine operation.