Analysis Of Bubbles Interaction And Motion Characteristics

Cavitation is a common phenomenon occurring in liquid circumstances.It is a complex two phase flow of multi-scale bubble dynamics.There are many characteristics such as unsteadiness and high nonlinearity as well as phase change process in cavitation.As a result,the mechanism of cavitation still lacks a comprehensive understanding.Most kings of cavitation consist of single and bubble pairs.The wall and bubble-bubble interaction has very important effects on the collapse process of bubbles.In this paper,we investigate the collapse of single bubble in high pressure surroundings near rigid wall or free surface and bubble pairs with different distance and phase based on the VOF method.Special attentions are paid on bubble shape,jet dynamics,collapsing time and phase transport.The collapse of single cavitation bubble in the infinite fluid field,basicly keep spherical shape.And its maximum internal pressure can be gathered on the smallest moment.Near the rigid wall,in the collapse of single bubble,cavitation bubble's far side gradually sag.Finally a jet is produced.Near the free surface,in the collapse of single bubble,cavitation bubble's near side gradually sag.Finally a jet is produced.In the collapse of bubble pairs with different distance,bubble pairs are breakdown by jet on the end of the collapse.A 3D planer bubble shape present.And a high speed jet can be gathered which speed can reach to 100m/s.This speed of jet decrease with initial distance of bubble pairs.Under the effect of bubble-bubble interaction,bubble pairs' distance decrease in the process of collapse.And on the collapsing moment,distance of bubble pair increase with initial distance of bubble pairs.In the collapse of bubble pairs with phase difference,in-phase bubble pairs generate symmetrical shape and jet under the effect of Bjerknes force.The direction of jet is towards to each other.A minimum distance and a maximun collapsing time of bubble pairs can be gathered.The out-phase bubble pairs generate generate dissymmetrical shape and jet.The direction of jet is away to each other.With phase difference increasing,distance and collapsing time of bubble pairs,respectively,decrease and increase.