RESEARCH ON DYNAMIC CHARACTERISTICS OF LARGE-SCALE MONOPILE OFFSHORE WIND TURBINE UNDER TYPHOON EVENT

Large scale wind turbine is an important direction of offshore wind technology in China. The southeast coast is a vital base for the development of offshore wind. However, the impact of typhoon events, which frequently occurs in this area, can not be neglected. The turbulent properties of typhoon are different from the normal strong wind. Meanwhile, the high wind speed during the typhoon events can lead to large typhoon waves. The aim of present work is to study the dynamic characteristics of the large scale monopile offshore wind turbine (OWT) during different typhoon stages, considering the unique wind and wave fields caused by typhoon. The DTU 10 MW monopile-type OWT were investigated using an integrated software, Simulation Workbench for Marine Application (SIMA) and the numerical model is established. The results show that pitch control can effectively reduce the wind loads on the blade during the typhoon event, and the wind loads on the turbine supported by monopile foundation mainly comes from the tower. At the different stages of the typhoon, the large-scale monopile offshore wind turbine exhibits different dynamic characteristics. The tower movement during the entire typhoon process is controlled by the first-order nature frequency which was excited by waves. The dynamic load of the structure above the tower base is dominated by inertial loads. The response energy growth rate at the first-order frequency of the tower movement is decreasing as the wind speed is increasing. And the response energy transfer to low frequency and wave frequency. The dynamic load under the base is obviously affected by wave load and wind load, shear response is controlled by wave frequency while bending moment response is controlled by first order eigen frequency and it is also greatly affected by the wave frequency and low frequency induced by wind at the mudline below tower base.