Study On The Coupled Motion And Performance Of Mushroom Wave Energy Conversion

In recent years,wave energy utilization has become a global research hotspot.There are many kinds of wave energy converters,and scholars all over the world are actively exploring the analysis methods of wave energy devices with high energy conversion efficiency.In this paper,the mushroom wave energy conversion system is taken as the research object.Due to the mutual coupling of hydrodynamics,motion,force and energy transfer between the cylinder and the buoy,new uncertainties occur in its motion response,load characteristics and energy conversion characteristics.Therefore,it is necessary to study and explore carefully in academia.Firstly,based on the Eigenfunction Expansion-Matching(EEM)of potential flow theory,the first-order diffraction and radiation problems of mushroom wave energy conversion device under linear wave conditions are analyzed in frequency domain,and the analytical expressions of wave loads and hydrodynamic coefficients acting on the mushroom are derived,and combined with the specific examples to analyze the hydrodynamics of the device.On this basis,the time-domain semi analytical expressions of wave excitation force and hydrodynamic coefficient are obtained by using the Impose response function of nonlinear(IRF)in the frequency domain to time domain method.Then,a simplified mathematical motion model is established for the mushroom wave energy converter,and a linear Power Take-off(PTO)system is introduced to derive a coupled nonlinear motion differential equation system containing only two degrees of freedom unknowns.The fourth-order Runge-Kutta Methods(RKM)with fixed time steps is used to solve the numerical solution of the equations of motion by writing an Intel Fortran programs.Based on the existing model test data,the mathematical model of this paper is compared and analyzed to verify the feasibility of the theoretical calculation method of hydrodynamics,motion and wave energy conversion.Finally,the appropriate regular incident wave is selected to solve the time-domain motion and wave energy conversion characteristics of the mushroom wave energy device,and the coupling effect is numerically analyzed.The influence of the linear PTO damping coefficient on the motion and power generation performance of the device is studied.The research results of this paper lay a technical foundation and scientific basis for further practical application.