Numerical Simulation Of A Cavitation Bubble And Cavitation Water Jet

With the increasing development and progress of science and technology,cavitation water jet,as a new and advanced surface treatment technology which has a very good prospect in the industry,is widely used for cleaning and derusting,peening,environmental chemical engineering,and oil production.According to the cavitation erosion principles of hydraulic machinery and taking the advantage of the high pressure caused by the collapse of the artificial cavitation bubbles within the water jet stream,the attempt to improve the work effect of cavitation water jet is carried out.Compared to the common water jet,the nozzle operating pressure can be reduced by one or two order of magnitude,and the pressure on the target surface being treated can reach the level of GPa.Modeling of the collapse process of cavitation bubbles and the inner flow field of the nozzle,reveal the mechanism of cavitation water jet,and optimize the structure parameters of nozzle.The simulation of the features of the collapse of cavitation was performed by using VOF method.The predicted results are in good agreement with the experimental results.The investigation of the effects of the distance between cavitation bubble and the rigid wall(?),the size of cavitation bubble and ambient pressure on the collapse process of a single cavitation bubble near a rigid wall was conducted.Along with the decrease of ?,the asymmetric deformation of cavitation bubbles becomes more and more obvious,and the time from jet formation to final collapse increases,both maximum jet velocity and collapse pressure decrease.The size of cavitation bubble has insignificant effect on jet velocity and collapse pressure.The maximum jet velocity and collapse pressure increase significantly with the increase ambient pressure,and the increase of collapse pressure is even close to an order when ?=2.0.In order to obtain the optimal structural parameters of angle nozzle,the velocity field,the pressure field and the volume fraction of vapor were simulated by FLUENT software to study the influence structure parameters on the nozzle cavitation.The results show that the distance of convergent section has little effect on jet velocity and pressure drop at the cylinder section of nozzle,and the longer the length of the diffuser,the stronger the cavitation capacity of the nozzle,but the outlet jet velocity will be greatly reduced.Under the comprehensive evaluation,the optimum values of the shrinking angle,diffusion angle and the distance of cylinder section are respectively 30 o,15o and 1mm when the diameter of cylinder section is 1mm.