The Double Cylinder Caisson Is Also Used For Energy Conversion Research Of OWC Wave Power Generation Device On Shore

Oscillating Water Column is a kind of wave energy conversion device using air as medium.Because of its characteristics of simple structure,high reliability,good anticorrosion and long service life,it occupies an important position in the wave energy conversion device.But for the existing onshore OWC device,it still has the problem of high construction cost.In addition,due to the special structure of the oscillating water column,especially for the traditional square box type oscillating water column wave power generation device,the low bearing capacity of the air chamber is always the weak link of the oscillating water column.In extreme sea conditions,OWCs often capsize due to large wave loads,and breakwater has a strong ability to withstand wave loads.The combination of the two can both improve the stability of the device and reduce the power generation cost.With high conversion efficiency,Oscillating Buoy is widely used in practice,but its reliability is poor and maintenance cost is high.OWC gas chamber is also easy to be damaged under the action of waves in severe sea conditions.Therefore,it is considered that placing the oscillating float in front of the oscillating water column can absorb part of the wave energy in advance,reduce the wave load on OWC,and achieve the purpose of protecting the OWC air chamber.Based on the viscous computational fluid dynamics(CFD)theory and Star-CCM+computing platform,a three-dimensional CFD numerical model is established in this paper.Firstly,the wave verification of the numerical pool is carried out to ensure that the ideal wave parameters are generated at the device.Then the results of numerical calculation are compared with those of published papers to ensure the reliability of the calculated results.The effects of OWC geometrical parameters(opening Angle,opening height,upper opening size)on conversion efficiency of the single double cylinder were studied,and the wavefront characteristics of different monitoring points in the gas chamber and the effects of upper opening size on PTO damping characteristics were analyzed.Then,based on the numerical model in Chapter 3,a hybrid system model consisting of a double-cylinder OWC and a float OB is established.The grid independence and time step independence of the new model are verified to ensure the convergence of the calculated results.The optimal damping of float is calculated by potential flow theory and verified by viscous flow CFD theory.The damping characteristics of OWC in hybrid system are analyzed.The conversion efficiency of OWC and OB in hybrid system was compared with that of monomer.The characteristics of the wave surface in the OWC chamber and near the float and the influence of wave parameters on the amplitude of the physical parameters of the mixing system were analyzed under classical conditions.Then the effect of the ratio of float entry depth to OWC lower opening height and the ratio of float entry volume to OWC air chamber volume on the conversion efficiency of the mixing system was analyzed.Finally,the influences of the bottom shape of the float,the distance between the float and OWC and the radius of the float on the mixing system are studied.The results show that the numerical pool model based on Star-CCM+ can accurately simulate the interaction between waves and structures,and the CFD results are in good agreement with the experimental results.Through calculation,the wave surface of OWC chamber with single double cylinder has good uniformity and conversion efficiency,and its unique circular arc chamber front wall can effectively avoid the appearance of Seching phenomenon under most wave conditions.Compared with the traditional square box OWC,the double cylinder OWC has a smaller force on the front wall,and its combination with breakwater can not only reduce the power generation cost of OWC,but also improve the reliability of OWC and breakwater.In addition,OWCOB,a hybrid system composed of oscillating water column and float,further expands the range of wave energy absorbed by the device.Then,by optimizing the shape,position and radius of the float,the ability of the wave energy device to resist wind and waves is further improved.