Spherical tuned liquid damper for vibration control in wind turbines

A tuned liquid damper (TLD), which consisted of two-layer hemispherical containers, partially filled with water, was investigated as a cost-effective method to reduce the wind-induced vibration of wind turbines. A 1/20 scaled test model was designed to investigate its performance on the shaking table. Three groups of equivalent ground accelerations were inputted to simulate the wind-induced dynamic response under different load cases. The influence of rotors and nacelle was assumed to be a concentrated tip mass. A series of free and forced vibration experiments were performed on the shaking table. The experimental results indicated that the spherical TLD could effectively improve the damping capacity of the test model. The standard deviation of the dynamic response could be effectively reduced when the excitation frequency was approximately equal to its fundamental frequency. For overspeed and extreme operating gust load cases, the standard deviations of the dynamic responses were reduced more than 40% when the liquid mass was about 2% of the generalized mass; for parking load cases, the corresponding standard deviation was reduced more than 50% when the liquid mass was only 1% of the generalized mass. That is to say, the spherical TLD can effectively improve the anti-fatigue performance of the wind turbine tower.