自润湿液体过冷核态沸腾射液流现象分析

对比去离子水和应用具有自润湿特性的正丁醇水溶液，进行Marangoni效应对微加热面汽泡行为影响的研究。通过高速摄像技术观测到了去离子水中的泡顶射液流和正丁醇溶液中的多射液流现象。相应的数值模拟表明，Marangoni效应引起过冷去离子水从过热表面向泡顶流动，而引起正丁醇溶液向相反方向流动，即过冷溶液流向过热表面。多射液流现象持续时间比去离子水的长，还可引起泡底微液层的瞬时紊乱现象。多射液流现象发生时，汽泡附近的温度梯度较大，而速度梯度则接近垂直于加热表面。正丁醇溶液的模拟结果与实验观测一致，表明表面张力及所引起的Marangoni效应对分析不同流体的过冷核态沸腾机理至关重要。

Jet flow phenomenon during subcooled nucleate boiling of self-rewetting fluid

In this paper, a self-rewetting fluid, namely aqueous n-butanol solution, is employed for demonstrating the thermocapillary effect on bubble behaviors during subcooled nucleate boiling on thin wire by comparing with deionized water. Bubble-top jet flow for these fluids is observed around a platinum micro heated wire by high speed CCD camera. Corresponding numerical simulation proves that it is the thermocapillary convection that attracts the subcooled water to flow from the superheated microlayer at the base to the top of a stationary bubble. For n-butanol solution, however, the thermocapillary convection can induce it to flow oppositely, which causes the subcooled solution to flow onto the heated surface. The simulation for the solution is in good agreement with the experiment where the subcooled liquid near the bubble top flow towards the bubble base and hence multi-jet flows occur. The multi-jet flows can sustain for a long period and cause transient chaos at the superheated thin liquid layer near the heated surface. The temperature around the bubble presents sharp temperature gradient and the velocity in the near wall regionis almost vertical to the wall. The studies on the effect of thermocapillary convection are crucial to the mechanisms of subcooled nucleate boiling of fluids.