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

在1g和微重力（10 μ g）条件下，研究了微细异物颗粒在具有垂直温度的液体（蒸馏水和硅油）中的行为<-5>。在使用Toki市MGLAB的落轴进行的下落实验中，在硅油中不存在温度梯度时，由于达到微重力，1g以下的水颗粒在硅油中不断下落，然后停止。相比之下，当硅油中形成正温度梯度时，由于达到微重力，水颗粒在非常短的停止后向上移动。水粒子的上升速度随粒子半径和硅油中温度梯度的增大而增大，根据本课题组以往的研究分析，在粒子与液体的界面附近，温度梯度会产生界面张力梯度，促使粒子向界面张力减小的方向运动。根据我们的研究结果，定性地解释了颗粒速度随颗粒半径和温度梯度的变化规律。此外，本研究还表明，为了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，需要更长的微重力时间。抛物线飞行实验对于准确地阐明各种体系中异物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.