Numerical Simulation Of Mooring System And Structural Optimization Based On An Elliptical And Cylindrical Raft Wave Energy Conversion Device

As a high-quality marine energy,wave energy has being widely studied and exploited.It has been referred as a clean and renewable energy together with solar,wind and geothermal energy,and has a very wide application prospect.Raft-type wave energy conversion device is a typical type of device for capturing wave energy.By using articulated multi-float as the basic structure,it converses energy through the relative motion of the joints of adjacent floats.At present,there are many studies on the hydrodynamic performance of raft capturing devices,but few on the structural optimization and mooring system in specific sea state.Therefore,this paper,taking capture efficiency as the main reference factor,started with the structural parameter optimization and mooring system,compared the energy capture effects with different structural parameters,realized the optimization of structural parameters and the design of mooring system and carried out the following contents:1)The energy harvesting mechanism of elliptical and cylindrical raft wave energy conversion device was deduced.In order to solve the problem that the existing hydrodynamic theory cann’t accurately analyze the motion response of elliptical and cylindrical raft wave energy conversion device,based on Newton’s Law of Motion,Lagrange’s Equation,Rayleigh Dissipation Function and Catenary Theory,this paper used the motion mechanism of the horizontal cylindrical float for reference,and theoretically analyzed the hydrodynamic performance of the elliptical and cylindrical float and the motion response of the mooring system to the device from the angle of energy-motion law.What’s more,this paper also determined the capture efficiency as an index for evaluating the energy conversion efficiency of the device and various parameters required for designing the mooring system,which provides a theoretical basis for the full-text’s structural optimization research and mooring system analysis.2)The structural optimization of elliptical and cylindrical raft wave energy conversion device was studied.In order to solve the problem that the energy conversion efficiency of the same device is greatly different in different sea states and the structural parameters have a great influence on the capture efficiency,by using ANSYS-AQWA,a kind of finite element software,to model and simulate the device based on the boundary element method,taking the five wave conditions under the three sea state as the marine environment,this paper verified the accuracy of the model by comparing the previous research results,and determined the structural parameters of the device corresponding to the maximum capture efficiency under the three-level sea state by analyzing the capture efficiency corresponding to the structural parameters such as the length,section axis ratio,spacing,draught,quantity and height of center of gravity.3)Research on mooring system of elliptical and cylindrical raft wave energy conversion device was carried out.In order to solve the problem that the current wave energy conversion devices’ s mooring system is single form and simple function,based on the energy capture characteristics of raft wave energy conversion device,this paper designed five types of mooring systems based on catenary according to the mooring system of ocean platforms and ships.And this paper determined the optimal mooring mode of front-double and rear-single mooring lines mooring system by comparing and analyzing the capture efficiency of the device with these five kinds of mooring systems under the three-level sea state,which provides a reference for the design of mooring system of wave energy conversion device.