What does the critical wind speed of tower equipment refer to?
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1. What does the critical wind speed of tower equipment refer to?
The critical wind speed is also known as the resonance wind speed. In the subcritical and transcritical ranges, it is the wind speed that makes the frequency of vortex shedding approach the natural vibration frequency of the equipment.
The tower is always subjected to forces in the windward and crosswind directions, which correspondingly act as drag and lift. The latter is much larger than the former; therefore, only lift needs to be considered in the calculations. The lift acting on the tower is alternating, and its frequency is the same as the vortex shedding frequency. Therefore, when the vortex shedding frequency coincides with the natural frequency of any mode of vibration of the tower, it will cause resonance in the tower. The wind speed at which a tower resonates is called the critical wind speed. Tall slender towers usually have platforms installed to prevent resonance