Study On The Test Methods And Effects Of Ambient Parameters For The Laser-induced Cavitation Bubble

The effects of the ambient pressure and cone boundary on the laser-induced bubble’s dynamics behavior were investigated by the means of theory, experiment and simulation, such as the effects on the collapse time, maximal radius and the formation of liquid jet.The simulation model of the collapse stage of bubble close to a rigid boundary was created by methods of the Finite Volume Methods (FVM) and Volume of Fluid (VOF), and the effectiveness and reliability of the simulation work was also demonstrated by comparing with the results of the experiment and grid setting with different size. The first derivative of the function of the bubble wall of right neighborhood of center of the top bubble wall in the bubble vertical section was proposed as the numerical criteria of the jet formation.The optical beam deflection and the principle the detecting technique on the bubble radius based on the PBD were analyzed on the basis of the geometric optics method. The experimental criteria for judging the maximum bubble radius were modified using the principle of the unequal precision measurement, and the weighted mean value of maximal radius and its standard deviation were calculated out using this criteria, and the detecting efficiency was greatly raised.The effects of the ambient pressure on the bubble dynamics were investigated on the basis of theory, experiment and simulation. And the parameters of the bubble collapsing in the different ambient pressures, such as collapse time, maximal radius, the formation of liquid jet, the liquid impact force, were obtained by the experiment and simulation results. The results indicated that the maximal radius and collapse time both decrease nonlinearly with increasing of the ambient pressure, and the velocity of the center of the top bubble wall, liquid jet velocity at collapse and the impact force of liquid jet all increase nonlinearly with the ambient pressure. But the relative formation time of liquid jet and the displacement ratio of bubble center while the liquid jet has formed are independent with ambient pressure.The virtual plane boundary model for the bubble collapsing close to the cone boundary was created and the expression of the collapse time of the bubble was obtained by the methods of the data fitting. The collapse time and the profile of the bubble collapsing in the vicinity of the cone boundary with different cone angles were obtained through experiment and simulation work. The results indicated that the effects of the cone boundary increase with the cone angle of the cone boundary. The degree of the departure of bubble shape from sphericity, collapse time, the displacement ratio of bubble center and the bubble volume at the collapse time is greater near the cone boundary with the bigger cone angle. And the cone boundary with a bigger cone angle could make the bubble to form an effective liquid jet. The effects of the cone boundary on the bubble increase with the decreasing of the dimensionless distance, but independent with the maximal radius for the same cone angle.The conclusion of this dissertation is useful for theory of the cavitation and cavitation erosion and helpful for the application of the high temperature, high pressure and liquid jet induced in the bubble collapse stage into the scientific research, industry and other filed. The results also provide the theoretical and experimental reference to laser processing, laser medical treatment and laser propulsion underwater.