Model tests on large-diameter monopile-supported offshore wind turbine in sand

Using the motor servo random dynamic loading equipment, a series of 1g model tests are carried out to investigate the dynamic response characteristics of the monopile-supported wind turbine model in sand under storm conditions. The experimental results indicate that the extreme displacement response of the blade-coupled model is about 4%~8% smaller than the lumped model. The lumped model contains a single resonance peak corresponding to 5 Hz. However, the blade-coupled model contains two natural frequency resonance peaks 4Hz and 6Hz, which are corresponding to the natural frequencies of the tower and the blade-tower coupling respectively. With the increase of the average wind speed under storm conditions, the extreme displacement response shows a non-linear growth trend. For the bottom-fixed model, the extreme displacement response of the tower tip is about 45% lower, and the natural frequency is about 11% higher compared with the monopile foundation model. For the wind spectrum with higher energy level and more high-frequency distribution, the corresponding extreme dynamic response and the energy level in the frequency domain are higher.