Movement of Foreign Particles in Liquid Driven by Interfacial Tension Gradient under Microgravity

研究了在1g和微重力(10^&lt；-5&gt；g)条件下，细小杂质颗粒在垂直温度下液体(蒸馏水和硅油)中的行为。在东京MGLAB降落轴的跌落实验中，硅油中不到1g的水颗粒在达到微重力时陷入停顿，硅油中不存在温度梯度。相比之下，当硅油中建立了正的温度梯度时，水颗粒在非常短的停留时间后被发现向上移动，因为达到了微重力。水颗粒在硅油中的上升速度随颗粒半径和温度梯度的增大而增大，本课题组在前期研究的基础上进行的分析表明，在颗粒-液体界面附近，温度梯度会导致界面张力梯度，从而推动颗粒朝着降低界面张力的方向发展。在前人分析的基础上，定性地解释了粒子速度对粒子半径和温度梯度的依赖关系。此外，这项研究还表明，需要更长的微重力周期才能更清楚地阐明界面张力梯度对液体中外来颗粒行为的影响。抛物线飞行实验对于准确阐明各种体系中外来颗粒在液体中的行为具有更大的可行性。

The behaviors of fine foreign particles in liquids (distilled water and silicone oil) with a vertical temperature were investigated under 1g and microgravity (10^<-5>g). In a drop experiment using a drop shaft of MGLAB in Toki city, water particles, which had kept falling down in silicone oil under 1g, came to a standstill as microgravity was reached when no temperature gradient existed in silicone oil. In contrast, water particles were found to move up after a very short stop as microgravity was reached when a positive temperature gradient was built up in silicone oil. The upwards velocity of the water particle show a tendency to increase with increasing radius of the particle and temperature gradient in the silicone oil.Analysis based on the previous study by our research group indicated that around the interface between particle and liquid, temperature gradient could result in interfacial tension gradient that propels particle in the direction of decreasing interfacial tension. The Dependencies of the particle velocity on the radius of the particle and the temperature gradient are also explained qualitatively based on the analysis using our previous study. In addition, this research also indicates that a much longer period of microgravity is needed in order to clarify more clearly the effect of interfacial tension gradient on the behavior of foreign particles in liquid. A parabolic flight experiment has much more feasibility for clarifying accurately the behavior of foreign particles in liquid for various kinds of systems.