Dynamic Response Analysis Of Offshore Wind Turbine Foundation Based On Apparent Fixity Model

Due to the increasingly serious environmental pollution and energy depletion caused by the use of fossil energy,the development of green renewable energy has become an important means of sustainable economic development in many countries,and the concepts of energy conservation,emission reduction,and sustainable development have been widely recognized by all sectors of society.Wind power is second only to hydropower,accounting for 16% of the world’s renewable power generation.In the energy development plans of various countries in the world,renewable energy has occupied an increasingly important share,and has become an important direction for future energy utilization.Among them,wind energy has attracted many countries’ attention due to its large scale,rich reserve,wide distribution and high values of commercial development.As offshore wind power gradually moves towards the deep sea,the monopile foundation,the most common form of wind turbine foundation,has a growing pile diameter.However,the current researc h on the role of soil-structure in the monopile foundation structure of large offshore wind turbines is still immature.Therefore,based on HAWC2 software,this article intends to conduct in-depth research on the dynamic response of the soil-structure interaction of the giant diameter pile foundation of the offshore wind turbine for the 10 MW large offshore wind turbine and the complex soil environment,revealing the interaction mechanism of the flexible monopile foundation of the soil and the super large diameter(diameter>8 m).The research has far-reaching theoretical and engineering application values for the safe operation and cost control of wind turbines.The main research contents of this paper include:(1)A suitable single pile foundation is selected based on the IEA10 MW onshore wind turbine model,and a 10 MW offshore single pile wind turbine numerical model is established in the wind turbine full coupling analysis software HAWC2.The results are compared to verify the correctness of the wind turbine model.The responses of the structure are analyzed for both normal operational and extreme condition.(2)Based on the apparent fixity theory and rigid foundation theory,the soil-structure interaction is simulated.Taking the offshore 10 MW monopile wind turbine as the research object,considering the coupling effect of the simple harmonic wave motion of the monopile wind turbine and the wind load,The dynamic response and transient dynamics of the 10 MW large pile diameter wind turbine were compared and analyzed.The natural frequency,static characteristics,and the dynamic responses of the large diameter fixed single pile wind turbine under simple loading conditions were carried out,focusing on the change of tower top displacement,the loading at the tower foundation and the mud surface.The rigid foundation and apparent fixity methods,which are commonly used in engineering application,are utilized to analyze the model.The calculated results of the two methods are compared;the effects of different soil-structure interaction models on natural frequencies,vibration modes,and tower bottom,and the impact of the tower top dynamic responses are studied.(3)Under the combined effect of wind and waves,the dynamic response analysis of monopile wind turbines is carried out.The wind turbine analysis software HAWC2 is used to establish a fully coupled numerical model of the rigid foundation and apparent fixity model.The results are analyzed in time domain and frequency domain under a variety of typical environments.The dynamic responses and structural loads at the main nodes of a 10 MW offshore wind turbine are studied,mainly concerning the rotor thrust,blade root shear and bending moment,tower base shear and bending moment,wind turbine shear and overturning moment of the monopole wind turbine under the combined effect of wind and waves for the ordinary and severe sea conditions.