Consideration in further experimental investigation of thermocapillary drop migration
- Paper number
IAC-06-A2.2.04
- Author
Mr. Jingchang Xie, Chinese Academy of Sciences, China
- Coauthor
Mr. Hai Lin, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Mrs. Pu Zhang, Institute of Mechanics, Chinese Academy of Sciences, China
- Coauthor
Dr. Wen Rui Hu, Institute of Mechanics, Chinese Academy of Sciences, China
- Year
2006
- Abstract
The drop shaft experiments and the space experiment were conducted on the thermocapillary drop migration at large Marangoni numbers, Ma, in the past years. Through these experiments, non-linear behaviors of thermocapillay drop migration are studied. The experimental results show that the migration velocities at large Ma are much smaller than that given by the YGB linear model and there are discrepancies between the experimental data and the current theoretical predictions, e.g. the ones from numerical and asymptotic solutions. Further analysis has been made recently based on the experiment results. When comparing these experiment results, we noticed some different phenomena except the similarities between the different experiments. In the drop shaft experiment, it is observed that the thermocapillary migration velocities of different drops almost have reached their steady velocities, and in this case the maxim Marangoni number is 1900. We can obviously see the drop migration process that the drop accelerate first and then generally decelerate towards a steady velocity during 4.5 seconds microgravity duration offered by the drop shaft facility. For the space experiment conducted aboard Chinese ShenZhou spacecraft however, only the transient migration velocities can be obtained, in which the value range of Ma is from 200 up to 5500. Thus, difficulties would be raised to get the benchmark data and make comparison with other experimental results or related predictions. Thereby, how to explain the reasons of these difference and obtain the steady velocities of drop migration at large Ma experimentally is what we are most concerned with. In this paper, we have analyzed in detail the process of the experiments and discussed the possible factors which may effect the attainment of the steady migration velocity in the space experiment, including the selection and application of the temperature gradients imposed, the coefficient of interfacial tension with temperature of drop and matrix liquid phases, the drop size and the correlations among them. The impact of miscibility of the liquids on the drop migration process has also been discussed, giving the evidence of miscibility of silicone oil and FC-75 Fluorinert liquid, though the two liquids are always regarded as immiscible ones. Moreover, the consideration in the design and objectives of next space experiment of thermocapillary drop migration at large Ma are also introduced in here.
- Abstract document