粘性液体空化初生的空泡动力学分析

Analysis of Bubble Dynamics during Cavitation Inception in Viscous Liquids

摘要:

基于 Rayleigh-Plesset（R-P）方程，对粘性液体中空泡平衡的稳定性，空泡爆发过程，以及爆发强度（由最大发展速度表征）进行了分析。稳定性分析表明：空化初生时，不可凝结气体不可或缺，而且应处于等压和等温过程之间，即多方指数应处于（0，1）之间，这意味着空化初生由质量扩散和传热共同主导。 尤其空化初生刚开始时，该过程逼近于等压过程。通过计算强烈空化时的空泡早期发展过程可以推测，空化初生时，液体表面张力的作用很弱，表面张力的作用只在空泡发展的中后期呈现出来。另外，气泡在局部最小尺寸附近的最大发展速度和最大溃灭速度的表达式表明，两者的差异程度只与液体粘性效应有关。

Abstract:

Based on the Rayleigh-Plesset（R-P）equation，the balance stability，development history，and cavitation intensity（represented by the maximum expansion speed）of bubbles in viscous liquids are analyzed. Stability analysis indicates that incondensable gas is indispensable during cavitation inception，and its polytrophic index falls within the range（0，1），indicating that cavitation inception is governed by both the mass diffusion of incondensable gas and heat transfer between the liquid and the bubble. Particularly，at the initial stage of cavitation inception，the thermodynamic process closely resembles an isobaric process. By calculations of the intense developments of cavitation bubbles，it can be inferred that the effect of surface tension is weak during the stage of cavitation inception but it becomes evident in the middle and late stages of the development. Additionally，the maximum expansion and collapse speeds near a local minimum bubble size are formulated，and their difference is found to depend on the effect of liquid viscosity.