汽泡间的碰撞、合并和绕流现象与数值研究

Numerical Investigation on Bubble Collision,Coalescence and Circling Phenomena

微尺度物体表面过冷沸腾中,汽泡间的相互作用对于传递现象起着重要的作用.本文通过实验观测到微尺度铂金加热丝表面高纯水过冷沸腾过程中汽泡的碰撞,并进行相应的数值模拟.模拟结果表明,汽泡合并过程中表面张力发挥着重要的作用;汽泡的分离是表面张力和热毛细作用的共同结果;小汽泡与大汽泡碰撞后可能发生绕流,此时动量交换很小,界面张力和热毛细力起主要作用,小汽泡在大汽泡顶部停留数毫秒后与大汽泡合并或脱离。模拟结果与实验结果一致.

The interaction between adjacent bubbles plays an important role in transport phenomena when subcooled boiling occurs on a micro heated source. In this study, bubble collision during sub- cooled boiling on a platinum microwire submerged in ultrapure water is investigated experimentally. The experimental result is compared correspondingly with a numerical analysis. The simulation shows that the surface tension plays an important role in bubble coalescence. It also indicates that both the effects of surface tension and thermocapillary force contribute to bubble separation. Small bubble can circle a bigger one after collision, when the momentum to be exchanged is small and the interracial tension and thermocapillary force play important roles in the circling process. Small bubble can stop on top of a bigger one for a few milliseconds, and then bubble coalescence or collapse may happen. The simulation is in good agreement with the experiment.