The Analysis Of Diffraction And Heave Dynamic Performance For A Floating Wind Turbine Platform Supported By Aircushion

With the exploitation of offshore wind power going from shallow water to deeper seas,this paper presents an aircushion type wind turbine support platform which can be applied to seas with depth of 30-100 m supported by the national Natural Science Foundation of China.To research the diffraction and heave dynamic performance of this air cushion type support platform,the main difficulty lies in the existence of internal free surface between gas and liquid.Based on linear potential flow theory,this paper firstly introduces a method of numerical calculation which can be applied to frequency domain analysis of floating structure supported by aircushion in the regular wave.Then the paper solves diffraction problem between the double vertical plates which has the same problem of internal free surface with the method of separating variable.The rationality of the analytical method is verified by comparing with the computational results of the numerical method.Afterwards the paper deduces the analytical solutions for the diffraction problem of two-dimensional rectangular floating structure supported by aircushion.Next,the paper studies the variation of internal free surface wave making and internal pulsating pressure along with the frequency change of incident wave by conducting the diffraction model test of rectangular floating structure supported by aircushion.The reliability of numerical calculation method is verified and the relationship between wave making of internal free surface wave and the pulsating pressure is analyzed by the test results.Then the paper compared the influences on the internal wave making of the height of air chamber and the air chamber is sealed or not.Finally,to research the heave performance of an air cushion supported offshore floating wind power platform,aerodynamic coefficient of aircushion which has the shape of circular,annular and fan-shaped annular is deduced in succession based on the linear theory of gas dynamics.Variations of RAO for the platform heave motion and internal pulsating pressure along with the frequency change of regular incident wave is calculated by solving the equation of motion in frequency domain for the air cushion supported floating structure after substituting aerodynamic force coefficient into the equation.Then the paper calculates andcompares the heave performance between aircushion supported floating platform and corresponding moonpool type floating platform and the real floating platform which is sealed at the bottom.Furthermore influences on heave performance aircushion supported floating wind power platform and internal pulsating pressure of height of air chamber,the initial position of internal free surface and working depth of platform are studied.To avoid period of platform motion and period of incident wave are close,the natural frequencies of platform’s heave motion under different working conditions are particularly analyzed...