Study On The Mechanism And Suppression Methods Of The Oscillation Buoys' Water Entry Impact

With the advent of the world energy crisis,humans began to attach importance to the research and development of new energy.Marine Energy as a renewable energy with large reserves,low cost,no pollution,etc.As a kind of Marine energy,wave energy is one of the highlights of research and development at home and abroad.Buoy is widely-used in wave energy power generation project as common element,which is often designed to maximize power absorption as the optimization goal,but ignored entry water impact factors.When the buoy gets out of the water for some reason and then re-enters the water,it will suffer from the water impact.The entry water impact will cause buoy to plastic deformation and fatigue damage,has a great influence on buoy working performance and life,So it is necessary to research into water impact mechanism,and put forward measures of reducing the water impact to prolong the life of buoy and reduce the loss.This article reviews the domestic and foreign research progress in entry water issues,Based on computational fluid dynamics CFD software Fluent has carried on the simulation study and the experimental study for different shapes of two-dimensional buoy at same time.Buoy shape including the two-dimensional conical buoy with the inclined angle of 30 °,45 °,60 ° and two-dimensional ellipsoidal buoy with aspect ratio c of 1/3,2/3,1,4/3,5/3,and two-dimensional cylindrical buoy.Conical buoy with the inclined angle of 45 °,hemispherical buoy and cylindrical buoy has carried on the experiment.The experimental data and simulation data match well,which verify the validity of the simulation.Through the analysis of spatial and temporal variations of pressure distribution and acceleration changes over time in the process of the different sha pes buoy into the water.we can come to the conclusion: The bottom of the buoy is most affected by the entry water impact in the process of buoy into the water,the peak pressure will move to each side in the water and pressure peak value increases in the process of transfer,the interval between the moment of two-dimensional conical buoy pressure peak and the moment of acceleration peak increases with the increase of helical angle.The influence of the air cushion effect intensity is different in the process of the different shapes buoy into the water.The order from weak to strong is two-dimensional conical buoy,two-dimensional ellipsoid buoy,two-dimensional cylindrical buoy.In this paper,the innovation points:(1)Considered the air cushion effect,using numerical simulation and experiment systematically studied and analysis of spatial and temporal variations of pressure distribution and acceleration changes over time in the process of the different shapes buoy into the water and in the transverse comparison between different types of buoy.(2)Making use of the effects of air cushion,the method of inhibit impact with buoy into the water is put forward.