Study On Hydrodynamic Performance And Energy Conversion Efficiency Of A Three-Dimensional Two-Body WEC

With the increasing consumption of fossil fuel,global warming and environmental pollution have emerged as an urgent environmental problem.Meanwhile,because of the limited access of fossil fuel,searching for alternatives to fuel the progress of human civilization has become an economic and social problem.However,the solution of environmental,economic or social problem depends on the advancement of science and technology.As a green fuel of abundant reserve,wide distribution and high energy density,wave energy has been studied by many countries around the world.In this paper,a three-dimensional two-body WEC(Wave Energy Convertor),consisting of a floating floater and a submerged damping plate,has been studied.The coupling hydrodynamic properties and energy conversion efficiency are also studied.Research is carried out as follows:Firstly,the research background and research significance of WECs are given comprehensively.After discussing the pros and cons of different devices,a two-body point-absorbing WEC is introduced,and the research object of this paper is therefore chosen.Secondly,based on the potential theory and decomposition method,three-dimensional fully nonlinear and linear numerical models of the two-body WEC are established.For the nonlinear model,the incident wave is given by the analytical solution of fifth-order Stokes wave;The Mixed-Eulerian-Lagrangian(MEL)method is used to update the instantaneous free water surface;The high-order boundary element method is adopted to realize numerical discretization;And the free water surface boundary conditions and the body motion equations are integrated by the fourth-order Runga-Kutta method.The auxiliary functions are introduced to decouple two kinds of couplings,the coupling between bodies and water,and that between two bodies.Besides,the energy absorbing efficiency equation of the two-body WEC is deduced.Based on frequency-domain theory,the optimal damping coefficient is also deduced and compared to the time-domain results,and the correctness of the established numerical model is verified.At last,the influence of the various parameters and nonlinear factors on the energy converter is studied for the guidance of design.