Visible Experimental Study Of The Cavitation Bubble Dynamics Near The Wall And The Membrane With The Discussions Of Membrane Cleaning Mechanisms

The dynamic behaviors of the cavitation bubble show the various characteristics(e.g.multiphase flow and high-speed jets)under the complex boundary conditions.Therefore,the collapsing mechanism of the bubble is complicated and needs to be further studied.In this paper,based on high-speed camera experimental system,the dynamic process of a single cavitation bubble collapses near the border of the rigid wall and the elastic membrane are studied in detailed.Particularly,the collapse process of the cavitation bubble is shown through a large number of experimental images.Additionally,a series of analysis parameters are defined to quantitatively analyze the dynamic characteristics of the cavitation bubble.The specific works could be summarized as follows:Firstly,the bubble collapsing in the symmetrical position to the border of the rigid wall are experimentally investigated.Based on the non-dimensional number ?,the collapse process could be catalogued into three cases.Furthermore,the movements of the bubble-liquid interface and the bubble centroid,the collapse time,and the non-spherical characteristics of the bubbles are quantitatively analyzed.The study indicated that the displacements of the bubble-liquid interface and the expansion speed show the obvious differences for the three cases.In addition,the ranges of centroid movement are significant with the medium value of a.The"retardant effect" of the bubble collapse is the most obvious with the small value of a.In the analysis of the non-spherical characteristics,the motion speed of the bubble-liquid interface is faster in the final stage of the bubble collapsing.Secondly,the bubble collapsing in the asymmetrical position to the border of the rigid wall are studied in detail.The experimental phenomena are clearly compared with the bubble in the symmetrical position.Furthermore,the quantitative analysis for the jet conditions and the centroid movement are shown.The research show that the bubble cluster phenomena could be catalogued into two modes with the transitions of the controlled parameters.Additionally,the direction angles of the jet obviously decrease with the increase of the non-dimensional number ?;the movement angle of the bubble centroid has the same trend with the increasing of the angle between the cavitation inception position and the symmetrical line(?).Finally,the mechanism of the cavitation bubble in the cleaning of elastic membranes are studied.The effect of pollutants on the dynamic behaviors of cavitation bubble is illuminated.Then,the experimental phenomena with different non-dimensional distance and thickness are qualitatively discussed.The study indicates that the dynamic behavior of cavitation bubbles is not affected by the presence of pollutants.With the variations of the non-dimensional distance,three typical processes are shown with the discussion of the relative cleaning mechanism.Additionally,the thickness of the elastic membrane is closely related to the damage of the membrane.