STUDY ON INFLUENCES OF TYPHOON NON-STATIONARITY ON DYNAMIC RESPONSE OF OFFSHORE WIND TURBINE WITH STEEL LATTICE FLOATING FOUNDATION

This study proposed a new type of steel lattice floating foundation for offshore wind turbines, and investigated the motion and dynamic responses of the steel lattice floating foundation for the offshore wind turbine during the passage of typhoon winds. A new type of steel lattice floating foundation was initially designed, considering a 5 MW wind turbine proposed by National Renewable Energy Laboratory (NREL). The dynamic response characteristics of the floating foundation were analyzed by Blade Element Momentum (BEM) theory, potential flow theory and Morison equation under the coupled typhoon wind-wave loads, using Holland typhoon model and the field data of super-typhoon "Mangkhut" (1822). The results show that the dynamic responses of the steel lattice floating foundation were significantly affected by strong typhoon, which were predominantly greater than those under synoptic strong wind conditions and featured with apparent non-stationarity. The dynamic responses of the floating foundation were in a good correspondence with the trend of the non-stationary wind speed. When the wind direction constantly changed, a greater torque was resulted at the bottom of the wind turbine tower, and increased yaw motions were also observed. It proves the effects of non-stationary typhoon winds on the stability of steel lattice floating foundation are indispensable and provides a theoretic basis and analysis methodology for the safety evaluation of steel lattice floating foundation for offshore wind turbines under typhoon winds.