液滴热毛细迁移问题的研究进展

THE PROGRESSES OF DROP THERMOCAPILLARY MIGRATION RESEARCH

液滴或气泡的迁移现象无论是在流体力学的基础研究中,还是在材料加工,化学工程等实际应用中都是一个很重要的课题.在微重力环境中,如果液滴或气泡所在的母液中外加一个温度场,则液滴或气泡就会由于表面张力分布的不均匀而发生迁移运动.这种运动被称为Marangoni迁移或热毛细迁移运动.综述了液滴或气泡的热毛细迁移问题历史研究中理论分析,数值模拟以及实验方面的主要结果,阐述了该问题的研究发展过程.目前液滴迁移问题的研究,理论分析解还只限于线性及弱非线性的定常问题,数值模拟工作已经得到了在热对流作用较小时液滴的非定常迁移过程,对于热对流影响很大的情况(Marangoni数大于100)则尚未得到与实验中观测到的相一致的理论结果.在总结前人研究的基础上,给出了热对流作用较大时液滴热毛细迁移非定常问题的最新的数值模拟结果,并对该问题在此情况下产生的新变化给予了分析.最后,分析了当前研究中所存在的问题并进一步展望液滴热毛细迁移问题未来的发展方向.

The migration of bubbles or droplets in liquids is a very important topic in materials science, chemical engineering and fundamental researches. Under the micro-gravity condition, if the temperature gradient of the background flow field is non-zero, bubbles or droplets will move because of differences in interfacial tension on the drop surface. Such motion is termed Marangoni migration or thermocapillary migration. In this paper, the progresses of researches on the drop/bubble thermocapillary migration, including theoretical analysis, numerical simulation and experimental studies, are reviewed. At present, the theoretical analyses mainly focus on linear or weak non-linear steady problems. Some numerical simulations were carried out on unsteady migration processes of drops with the Marangoni number less than 100. When the heat convection effect is strong（over 100）, no numerical results were reported that are consistent with those from experiments. In this paper, we summarize previous research results, give our new numerical results of unsteady drop migration problems with large Marangoni numbers and discuss new phenomena under this condition. Finally, some problems in current studies are pointed out and the development of drop thermocapillary migration problems in future is discussed.