The vibration mechanism of a parked wind turbine in a sheared inflow field

This study numerically investigates the vibration responses and underlying mechanisms of a parked National Renewable Energy Laboratory (NREL) wind turbine in a sheared inflow field, utilizing the Reynolds-Averaged Navier-Stokes (RANS) approach coupled with the Shear Stress Transport (SST) k-ω turbulent model, neglecting the effects of turbulent fluctuations in the oncoming wind. The results indicate that at a yaw angle γ = 45°, periodic vortex shedding occurs near the blade tip, with its frequency increasing approximately linearly with the inflow velocity. A significant 1st collective flapwise vibration is triggered when the vortex-shedding frequency approaches the blade's corresponding natural frequency, resulting in a maximum root-mean-square amplitude of 0.45 m and a peak amplitude of 0.81 m. With further increases in wind speed, the dominant vibration mode of the blade transitions sequentially from the 1st collective flapwise mode to the 1st flapwise tilt mode. Moreover, the vortex-induced vibration of one blade will excite strong coupled vibrations in the other two blades. These coupled flapwise vibrations further induce notable side-side oscillations in the tower. Finally, the vibration responses of both the blades and tower are highly sensitive to the blade damping ratio but only moderately influenced by the tower damping ratio. These findings confirm that the global dynamic behavior of the wind turbine is primarily governed by blade aerodynamics and structural coupling effects.