| The ocean accounts for about seventy-one percent of the total area of the earth,and it contains an extremely widespread and abundant marine renewable energy-wave energy which is contained in water in the form of kinetic energy and potential energy.Human beings have been developing and utilizing wave energy for a long time.Since the beginning of this century,wave energy utilization technology has once again become a research hot spot in the world.Three kinds of wave energy utilization technology,represented by oscillating water column,oscillating buoy and overlopping wave energy converter,and corresponding equipment industry chain have been gradually formed.Point-Absorption Wave Energy Converter(PAWEC)is a kind of oscillating buoy wave energy converter,which has become a widely concerned technology due to its technical advantages such flexibility of sea arrangement,wave adaptability and energy conversion efficiency.However,the kinematic and hydrodynamic characteristics in waves of PAWEC are very complicated,including hydrodynamic performance,wave energy conversion characteristics and the matching between them.So far,although PAWEC technologies have been extensively studied,there are still many fundamental or mechanical problems that have not been solved and need to be further research.For example,PAWEC dynamic characteristics time domain semi-analytical calculation method,the matching mechanism between the PAWEC hydrodynamic performance and nonlinear PTO system in time domain,the PAWEC hydrodynamic performance in irregular waves,possible coupling resonance mechanism of moon pool float and so on.Therefore,this paper,taking a series of typical point absorption wave energy conversion devices as the object,carries out the fundamental research on PAWEC dynamics and its characteristics based on the potential flow theory to lay a design foundation for the development of PAWEC technologies.For the hydrodynamic problem about PAWEC capturing energy,oscillatory motion model of wave energy buoy is established combined the vibration theory in the frequency-domain and time-domain analysis framework of potential flow theory.Based on the potential flow theory of Eigenfunction Expansion-Matching(EMM),diffraction problems and radiation problems of the float was deduced under linear wave conditions in frequency domain and obtained semi-analytical expressions for the hydrodynamic coefficients such as wave loading,additional mass,and radiation damping.On this basis,the time domain semi-analytical expression of the hydrodynamic coefficient of PAWEC is obtained by using frequency domain to time domain numerical solution of the Impose Response function(IRF)and coupled time domain motion control equations were established.By using fouth-order Runge-Kutta Methods(RKM),time domain motion and wave energy conversion characteristics of wave energy floats are obtained and the time-domain semi-analytical solution of the dynamic characteristics of the load,motion,and energy conversion has been developed.For the influence mechanism of the damping characteristics of the PTO system of the single oscillating float wave energy conversion device(PAWEC),it is currently decomposed into a linear damping for calculation,especially in the time domain analysis,the PTO system is more assumptions become a linear damping system for calculation so that the nonlinear effect is ignored.Therefore,the nonlinear characteristics of PTO system in PAWEC are considered,in this paper,the nonlinear PTO system is introduced into the time-domain solution to research the potential flow semi-analytical solution method of PAWEC nonlinear PTO system.Based on the potential flow theory analysis solution of EEM in frequency domain and numerical method of IRF,establishing the frequency-domain and time-domain coupled motion control equations solves this problem by iterating the characteristic parameter of nonlinear PTO system theoretical values.It provides the time domain solution for PAWEC hydrodynamic performance and nonlinear PTO system matching.In addition,for the analysis of the dynamic characteristics of PAWEC under the long-wave irregular wave,the statistical analysis of the spectral analysis method was used and the ISSC wave spectrum was used.Based on the potential flow frequency domain analytic solution of the feature function expansion and matching and the frequency domain to time domain numerical solution of the Impose Response function,the instantaneous motion response and instantaneous trap width ratio of PAWEC are obtained,and the PAWEC dynamic performance under different sense wave heights and peak periods is analyzed under irregular waves.In this paper,from the view of point absorbing wave energy conversion technology and the development of equipment,a highly efficient coupled wave energy absorption device based on the platform of the moonpool-wave energy float is proposed.From the perspective of dynamics,analyziing the Moonpool float is a hydrodynamic problem in which the wave and the moonpool platform and the wave energy float are coupled together.The relative motion,force and energy transfer between the moonpool platform and the wave energy float are mutually coupled.The complex coupling system makes the motion response,load characteristics and wave energy conversion efficiency of wave energy float appear new uncertainty,which requires in-depth and careful research and exploration in the academic field.In this paper,based on the theory of two-degree-of-freedom vibration,the coupled vibration model of the whole system is established.Through analytical solution based on the EEM and numerical solution based on the IRF,the semi-analytical solution of the dynamic time-domain characteristics about motion,load and energy conversion of the coupled system under the action of waves is developed,which lays a technical foundation and scientific basis for improving the overall performance of the moonpool-wave energy float system.Finally,based on the study of frequency domain and time domain,the semi-analytical theoretical method of the dynamic characteristics of the moonpool float wave energy conversion device is proposed.The design of the experimental model of the moonpool float wave energy conversion device and the pool test of dynamic characteristics are carried out.The dynamic characteristics of the Moonpool float wave energy conversion device are further studied.In order to explore the mechanism characteristics of the moon pool float wave energy conversion,this experiment is divided into two parts:one is the single float test without moon pool,and the other is the moon pool-float coupling test with moon pool.The moon pool structure is fixed relative to the earth.Through the model test of the Moonpool float wave energy device,the results of the semi-analytical theoretical method and the measurement results of the pool experiment are compared and analyzed.The wave energy conversion characteristics and resonance characteristics of the Moonpool float device are studied to improve the overall structure of the moonpool floating system.The performance lays the technical foundation and scientific basis. |
PDF Full Text Request