Hydrodynamics And Energy Characteristics Analysis Of The Dual-Resonance Point Absorber For Wave Energy Conversion

The ocean wave energy has the advantage of wide distribution,large amount of reservation and renewable.Thus,the development and utilization of the wave energy has great importance in terms of improving energy structure,developing the economy of the islands,and coastal defense,etc.The hydrodynamic characteristics are studied and analyzed for different convex-bottom cylindrical floaters which are normally suitable for the point absorbers.Based on the dual-resonance energy converting theory,a new concept of wave energy converter(WEC)is proposed,Sea-Dart Dual-Resonance Wave Energy Converter(SDDR-WEC).The wave energy conversion performance is studied numerically and experimentally,and a parameter-optimization design method is put forward.Based on the linear potential wave theory,linear wave-body hydrodynamics,analytical method for truncated cylinders,and linear frequency domain boundary element method,the hydrodynamic characteristics of convex-bottom cylindrical floaters are studied in non-viscous fluid.Combining the analytical method of truncated cylinders and the linear frequency domain boundary element method,a shape correction method is proposed to calculate the linear potential flow hydrodynamic coefficients of different convex-bottom cylindrical floaters.Using the viscous CFD method,which based on the RANS method,a linear viscous correction method is put forward to calculate the hydrodynamic coefficients of different convex-bottom cylindrical floaters.From the point of view of small viscous effect and construction easiness,the conical-bottom cylindrical floater is chosen after comparing the hydrodynamic characteristic of different convex-bottom cylindrical floaters.The linear viscous correction curves and formulas of the viscous hydrodynamic coefficients of flat-and conical-bottom cylindrical floaters are proposed.The conical-bottom cylindrical floater is chosen for the point absorber that discussed in this thesis,and named "Sea Dart".The dynamic model of the dual resonance energy converting system is established and studied.The motion and power response of the SDDR-WEC in the regular and irregular waves are studied with the consideration of the fluid viscosity.From the safety point of view,an end-stop concept is proposed and studied by non-linear impose response function(IRF)method.The numerical results show that the properly designed end-stop can effectively limit the excessive internal relative motion and have neglectable effect on the power response.Thus,the wave spectrum method can be employed to fast calculate the power response characteristics of the SDDR-WEC in the irregular waves.A parameter-optimization design method is put forward for the SDDR-WEC.The feature analysis and parameter optimization for PTO parameters(internal mass,spring,and damping)and geometry parameters(diameter and draft)are conducted by the spectrum analysis method and the general pattern search(GPS)algorithm.For a given sea area,aiming at the best annual averaged power,this method can find the corresponding optimal geometrical and PTO parameters.At last,a scaled model of the SDDR-WEC is designed,manufactured,and tested.The internal PTO system is tested on a specialized test-bench,and the whole system is in the wave tank.The key elements of the SDDR-WEC are the conical-bottom outer-floater(which is featured of small viscous dissipation),and the internal mass-spring-damping PTO system.The mechanical property of the internal PTO system and the response characteristics of the SDDR-WEC is studied.The experiments validate the feasibility of the concept,and the correctness of the theoretical methods,which lays the foundation for further practical application...