VORTEX INDUCED MECHANISM OF WIND TURBINE TOWER AND BLADE DURING SHUTDOWN
The phenomenon of vortex-induced mutual interference between the tower and blade exists in large-scale wind turbines,significantly affecting their safe operation.This paper investigates this characteristic by using the NREL 5 MW wind turbine as a model.It examines two-dimensional cross-sections where the tower and blade coexist at heights of 65,70,75,and 80 meters from the ground.Numerical simulations are conducted under wind conditions of 6,8,10,12,and 14 m/s,and the results are compared with those from single-tower conditions.The findings reveal severe mutual interference between the blade and tower wakes;compared with the single-tower condition,the pressure at a specific point on the tower increases by 1.5 times,and the lift coefficient experiences multiple magnitude responses,with its maximum being about 6 times that of the single tower.Additionally,the wake vortices of the tower and blade appear to merge and share the same frequency,enhancing vortex excitation.The vortex shedding frequency in the combined blade-tower condition is lower than in the single-tower case,making it more likely to synchronize with the lower-order natural frequencies of the wind turbine,thereby potentially increasing the risk of resonance.
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