Analytical Study On Hydrodynamic Characteristics Of Multi-body Wave Energy Device

Among various forms of wave energy power generation devices currently researched and developed,oscillating float wave energy devices have attracted extensive attention and research due to their simple structures,high energy capture efficiency and flexible layout.The research focus of wave energy devices is to reduce construction and operation costs,improve power generation efficiency and ensure the stability and reliability of system.Considering that the breakwater and wave energy devices have similarities in transforming incident wave energy,it has become an important direction for integrated utilization of wave energy which integrates wave energy devices into the breakwater in order to achieve system cost sharing and function diversification.Based on the current research status of relatively low capture energy efficiency and relatively narrow bandwidth of oscillating float wave energy device,this paper proposes a multi-body wave energy device system integrating oscillating float wave energy device and floating breakwater(i.e.,the multi-body system).Utilizing analytical research method,this paper explores the synergistic mechanism of multi-body system on wave energy capture,conducts intensive research on the hydrodynamic characteristics of systems under regular and irregular waves,which provides scientific theoretical basis for engineering design.The specific researches are as follows:Firstly,based on the theory of linear potential flow,an analytic model for the interaction between waves and multi-floating wave energy devices is established by utilizing the eigen-function expansion matching method;the velocity potential functions of each watershed are solved,the solution methods for vertical wave excitation force,additional mass and radiation damping of each floating body of the system are given,the expressions of the system's heave response amplitude operator,capturing width ratio,reflection coefficient and transmission coefficient are derived.Based on the verification of convergence,energy conservation and comparison of the simulation results with other published papers,the analytical model established in this dissertation is verified.Secondly,based on the analytical model,the hydrodynamic characteristics of the multi-body wave energy device under the action of regular waves are carried out.The effects of the width,draft,spacing,PTO(power take-off)damping,width ratio,draft ratio and number of floating bodies on the hydrodynamic characteristics of the system are investigated.In addition,the enhancement mechanisms of the system in wave suppression performance and wave energy capture characteristics are also explored.The results show that the peaks of the effective bandwidth and the total capture width ratio of the multi-body system are significantly larger than those of the traditional single-body system under the same volume,which can also maintain a higher capture width ratio(?>50%)in a larger frequency range and proves better performance in terms of wave attenuation and wave power extraction.Finally,under the effect of irregular waves,research concerning the hydrodynamic characteristics of multi-body wave energy device with different numbers of floating bodies is carried out.The differences of wave energy capture characteristics with the same structural parameters and the number of floating bodies under regular waves are compared and analyzed.Then the advantages of the integrated system in practical applications are proposed.The results indicate that the Bragg and floating body resonance phenomenons are weakened under the action of irregular waves,and the effective bandwidth of the multi-body system is larger.But the peak value of the total capture width ratio is smaller,and the differences of capture width ratios between adjacent floating bodies are reduced.