表面张力对近固壁二空化泡影响的数值研究

NUMERICAL INVESTIGATION OF SURFACE TENSION EFFECTS ON 2-D CAVITIES NEAR A SOLID WALL

在忽略浮力下，用边界积分方法数值模拟了表面张力对固壁之上且靠近固壁的二轴对称空化泡生长和溃灭的影响，发现在下空泡最大等效半径为上空泡一半情形，若固壁对下空泡的 Bjerknes 力大于上空泡对下空泡的 Bjerknes力，则表而张力的作用将使下空泡溃灭加速，使其向下的液体射流变强变宽；若固壁对下空泡的 Bjerknes 力小于上空泡对下空泡的 Bjerknes 力，则表面张力的作用将使下空泡溃灭变慢，使其向上射流变弱变细长；若这两个 Bjerknes 力近于相等，则表面张力将会对下空泡溃灭有重大作用，如改变下空泡射流的方向甚至形式(如由环状变向下或由向上变环状)．当上空泡等于或小于下空泡时，表面张力将不会对这两个空泡的行为产生显著影响．定性地分析了表面张力作用的机理．

When the effect of buoyancy force is neglected,surface tension effect on the axisymmetric growthand collapse of two cavities near and above a solid wall is investigated numerically by boundary integral method.It is found that when the maximal equivalence radius of the lower cavity is half of that of the upper one,surfacetension effect may cause the lower cavity collapse faster and its downward liquid jet stronger and wider if theBjerknes force of the wall to the lower cavity is larger than that of the upper cavity.And surface tension maycause the lower cavity collapse slower and its upward jet weaker,thinner and longer if the Bjerknes force of theupper cavity to the lower one is larger than that of the wall.In particular,surface tension may have substantialeffect on the collapse of the lower cavity such as change the direction or the form of the jet(from annular todownward or from upward to annular)if the two Bjerknes forces of the wall and the upper cavity to the lowercavity are nearly equal.When the upper cavity is equal to or smaller than the lower one,surface tension hasno significant effect on the behavior of the two cavities.The mechanism of surface tension effect is analyzedqualitatively.