稳定密度梯度中球形界面流动失稳的研究进展

RESEARCH PROGRESS ON THE MARANGONI INSTABILITY OF A DROP/BUBBLE IMMERSED IN LINEARLY STRATIFIED LIQUIDS

当流体界面上存在温度梯度或者浓度梯度时,会产生稳定或不稳定的界面流动.由于界面流动在多种工业过程中有广泛应用,其已经得到了广泛的研究.通常认为,在考虑界面流动时,体积力比如重力可以忽略,在小尺度下尤其如此.因此,稳定密度梯度的重力效应对界面流动的影响一直是被忽略的.然而,近期的一些研究表明,即使是在小尺度下,稳定密度梯度重力效应的影响也不可忽略.文章综述了稳定密度梯度中球形界面的流动及其不稳定性研究进展,介绍了球形界面的两种失稳模式——扩散受限导致的失稳与黏性受限导致的失稳,并且分析了对流、密度梯度、扩散、黏性,以及容器大小对流动失稳的影响.现有研究表明,在小尺度下,当流体界面有竖直方向的分量时,稳定温度/浓度梯度对界面流动及其稳定性的影响可能需要重新评估.最后根据现有研究的不足与发展动态,对未来的研究方向进行了展望.

Marangoni instabilities can emerge when a liquid interface is subjected to a temperature or concentration gradient.It has been extensively studied due to its wide relevance in industrial applications.It is generally believed that when it comes to Marangoni flows,bulk effects like buoyancy are negligible as compared to interfacial forces,especially on small scales.Consequently,the effect of a stable stratification on the Marangoni instability has been ignored.However,some recent researches have shown that even at small scales,the effect of stable stratifications cannot be ignored.This paper reviews the research progress on the Marangoni instability of a drop/bubble in a linearly stratified liquid.Two oscillatory instabilities,i.e.,diffusion-limited instability and viscosity-limited instability are introduced,and the effect of advection,density stratification,diffusion,viscosity and container size on the instability are reviewed.Current results suggest that when the interface is not horizontal at small scales,the effect of a stable temperature/concentration gradient on the Marangoni flow and its instability may need reconsideration.Further research directions are suggested based on the current studies.