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Clarification of flow transition of low Prandtl number liquid bridge by ultrasonic visualization

通过超声可视化阐明低普朗特数液桥的流动转变

基本信息

批准号：
17360087
负责人：
YODA Shinichi
金额：
$ 9.92万
依托单位：
Japan Aerospace Exploration Agency
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

Experimental and numerical study on Marangoni convection induced in low Prandtl number liquid bridge was carried out. In experiment, the transition from axisymmetrical steady flow to asymmetrical one which was estimated only by numerical simulation succeed to be detected firstly. Furthermore, the oscillatory transition with higher driving force was observed. The oscillatory flow was bifurcated with increasing the driving force of flow and finally chaotic flow was occurred. In numerical simulation, model taken into account of liquid bridge supporting rod which was simulated experimental condition was constructed. Temperature difference between supporting rods was gradually increased and transition process was analyzed. At first, straight shape of liquid bridge was calculated and the effect of aspect ratio (As=high/radius) on the transition condition was made clear across the wide range of As = 0.8-2.2. Moreover the oscillatory thermocapillary flow was analyzed by the proper orthogonal decomposition. As the result, spatio-temporal fluctuation of flow and temperature was precisely clarified. In the case of longer liquid bridge of As=2.0, influence of gravity and surface deformation on critical condition was discussed. It was firstly revealed that the critical temperature difference and oscillatory mode was changed depending on direction of temperature gradient and discrepancy from straight shape.

对低Prandtl数液桥中的Marangoni对流进行了实验和数值研究。在实验中，首次发现了轴对称定常流动向非对称定常流动的转变，这种转变是通过数值模拟来估计的。此外，还观察到了驱动力较大的振荡转变。随着流动驱动力的增大，振荡流动发生分叉，最终出现混沌流动。在数值模拟中，建立了模拟实验条件下的液桥支撑杆模型。支撑杆之间的温差逐渐增大，并分析了过渡过程。首先对液桥的直线形状进行了计算，在As=0.8~2.2的较宽范围内，分析了高径比(As=高度/半径)对过渡条件的影响。在此基础上，利用本征正交化分解对振荡热毛细管流进行了分析。结果准确地阐明了流量和温度的时空起伏。在AS=2.0长液桥的情况下，讨论了重力和表面变形对临界条件的影响。首次揭示了临界温差和振荡模式随温度梯度方向和与直线形状的差异而变化。