Research On Calculation Of Hydrodynamic Performance Of Multi-degree Of Freedom Buoy-chain-sprocket Wave Energy Device

With the implementation of China’s ocean development stratagem,the pace of ocean exploitation is accelerating.As a kind of ocean energy with large reserves,wide distribution,and high energy flow density,the exploitation and utilization technology of wave energy has been paid more and more attention by coastal countries around the world.Among many wave energy utilization technologies,oscillating buoy wave energy collection technology has become a research hotspot in the field of wave energy utilization due to its advantages of simple device structure,low operation and maintenance cost,good reliability,and high collection efficiency.Among them,the hydrodynamic performance calculation method of wave energy device is the theoretical basis for the optimization and control of wave energy device and the core scientific problem of wave energy utilization technology.Buoy-chain-sprocket wave energy utilization technology proposed by Shandong University belongs to oscillating buoy wave energy collection technology.The buoy-chain-sprocket mechanism is used to collect wave energy in this technology with good application prospects.Therefore,based on the linear potential flow theory,this thesis intends to use a combination of theoretical calculation research and physical model experiment research to study the hydrodynamic performance calculation method of buoy-chain-sprocket wave energy collection device,to provide a theoretical basis for the optimization and control of the prototype at the later stage.The main research contents of this thesis are as follows:1.The motion of buoy-chain-sprocket wave energy collection device under regular waves can be simplified to two degrees of freedom motion:the oscillation of the floating body along the guide rod and the pitch with the guide rod.To make full use of the indirect time-domain method to study and calculate the hydrodynamic performance of buoy-chain-sprocket wave energy collection device,the motion of the floating body is first simplified into three degrees of freedom motion:heave,surge,and pitch.And then the three degrees of freedom motion is transformed into two degrees of freedom motion by applying the motion coordination relationship to the three degrees of freedom motion.2.Based on the potential flow theory,eigenfunction expansion method and matching asymptotic expansion method are used to solve the frequency-domain wave-exciting force of the floating body in the direction of heave,surge,and pitch motion and the frequency-domain added mass and radiation damping of each motion mode of the floating body.Then,according to the Cummins method,a time-domain hydrodynamic motion differential equation that conforms to the floating body motion characteristics of buoy-chain-sprocket wave energy collection device is established,and the fourth-order Runge-Kutta method is used to solve it.To further improve the calculation accuracy of the hydrodynamic motion response,an improved calculation method is proposed for the time-domain wave-exciting force and the hydrostatic restoring force in the domain equation.Finally,the hydrodynamic response calculation of the device in frequency domain and time domain is completed by programming with MATLAB.3.The reliability of the frequency-domain hydrodynamic numerical calculation method of buoy-chain-sprocket wave energy collection device is verified by comparing the calculation results with the classical literature;the reliability of the time-domain hydrodynamic response calculation method of buoy-chain-sprocket wave energy collection device is verified by the physical model experiment of buoy-chain-sprocket wave energy collection device.Finally,the parameters of the prototype are optimized based on this calculation method,which provides a theoretical basis for the later development of the prototype.