Nonlinear vortex-induced vibration and its mitigation of wind turbines in parked conditions

This study aims to provide a comprehensive exploration of the nonlinear vortex-induced vibration (VIV) characteristics of the wind turbines in parked conditions. Considering the influences of the aero-damping and structure of the wind turbine, a vibration mitigation strategy for VIV is proposed to avoid the potential harm caused by VIV in practical projects. The finite element method (FEM) is used to analyze the mode of the wind turbine, and the aerodynamic performance of the wind turbine is analyzed by employing the blade element theory. Using the van der Pol equation for modeling fluid-structure coupling, a nonlinear equation for simulating the VIV of the tower, accounting for the aero-damping of the wind turbine, is established through the application of Hamilton's principle and the assumed mode method, and is solved by the method of multiple scales. The results show that the VIV in fore-aft bending mode direction of the wind turbine tower should be considered. The VIV of the wind turbine can be mitigated by changing azimuth angles and pitch angles. Furthermore, the effectiveness of the proposed vibration mitigation strategy is validated by the on-site vibration experiment.