Study On Hydrodynamic Optimization Of A New Arrayable Wave Generator With Extreme Wave Considered

Compared with other forms of marine renewable energy,wave energy has the advantages of high energy flow density and wide distribution.The space-time distribution characteristics determine the wave power technology has special advantages and broad application prospect in the resource exploitation of islands and far-reaching seas.However,the maturity of wave power device requires a long cycle of five stages,including theoretical research,preliminary design,numerical optimization,model experiment and actual verification.Meanwhile,the generating device may be subjected to destructive action of all kinds of extreme waves while obtaining wave energy.Therefore,at present,wave power products are often not scaled due to their low quality-value.Among the many technical difficulties restricting the industrialization of wave power device,the optimization of hydrodynamic performance is a key,which has important hydrodynamic theory significance and engineering significance.In this paper,a new airtight pneumatic two-float wave generator is studied,which capture energy through the relative heave motion between upper and lower float.The most direct influence on the absorption of wave energy by the device is the quality and shape design of upper float,and safety problem of extreme wave acted on device is also the most prominent.In addition,research on array of devices is of great significance to industrialization of wave power.In addition,considering that mooring plays a major role in limiting the horizontal position of wave device,in order to highlight the research focus of this paper,the influence of mooring is temporarily ignored.Firstly,in order to determine the optimal form of upper float is carried out,three simple and common shapes of upper float are selected in this paper,and influence of shape parameters of upper float on hydrodynamic response of two-float body with free heaving is analyzed and compared.Considering that the energy collection and output system is a linear spring damping system,motion equation of two-float system for heave in frequency domain is established and solved based on potential flow theory.Theoretical analysis shows that damping has great impact on the natural period and heave motion of system,while stiffness make little influence on them.Two-float system is further analyzed in time domain under regular waves by using AQWA,and heave motion response and the instantaneous absorption power of wave are obtained.In order to verify reliability of numerical simulation results,physical model experiments of three kinds of devices with different upper float under regular wave are carried out.Experimental results are basically consistent with the numerical results calculated in time-domain.Through above analysis,the optimal form of upper float is flat cylindrical float with suitable mass under the wave condition in this paper.Secondly,in order to consider the safety performance of two-float device under extreme wave action,the numerical model of freak wave based on a special kind of extreme random waves--freak wave generation theory is established by using Matlab.And then Analysis in time-domain is carried out by using AQWA-Drift that imports wave time history curve of freak wave based on the theory of freak wave.Heave response of two-float system is obtained and the reliability analysis is carried out.The results show that heaving displacement,velocity and wave force of system change dramatically,spring tension between the two floating bodies and cable tension of single point mooring system also change sharply at the moment of freak wave action.These are extremely detrimental to the reliability of system.Based on calculation results,the reliable suggestions for device strengthening are given.Finally,considering scale industrialization of wave power technology,numerical simulation of the optimization study of array wave power device is carried out in frequency domain and time domain for linear,rectangular and circular array by using AQWA on the basis of hydrodynamic optimization analysis of two-float system.The study dealt with the effect of different array,layout space and wave parameter on the motion response and the conversion efficiency of array system.Eventually,circular array with appropriate spacing is determined to be the most ideal array model under the wave condition in this paper.In this paper,hydrodynamic performance of a new type of two-float wave power device under different wave conditions is analyzed by theoretical analysis,numerical calculation and physical model experiment.Researches that include optimization of different floating body form and array form,safety and reliability of extreme wave are carried out.The final research results and suggestions can provide meaningful scientific reference for the research and industrial development of wave power in China.