Particle Accumulation Structures in a 5 cSt Silicone Oil Liquid Bridge: New Data for the Preparation of the JEREMI Experiment
Particle Accumulation Structures in a 5 cSt Silicone Oil Liquid Bridge: New Data for the Preparation of the JEREMI Experiment
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DOI：
10.1007/s12217-021-09879-3
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发表时间：
2021-04-01
影响因子：
1.8
通讯作者：
Lappa, Marcello
中科院分区：
文献类型：
--
作者：
Capobianchi, Paolo;Lappa, Marcello
在时间周期流动的驱动下，悬浮中的固体颗粒系统往往会在载体流体中产生让人联想到高度规则的几何物品的结构。按照这一思路，本研究提供了数字结果，以支持计划在国际空间站上执行的空间实验Jeremi(日本和欧洲关于Marangoni流动不稳定性的研究实验)。这个问题是通过求解空间中将建立的相同条件(微重力、5 cst硅油和不同液桥长宽比)下的非定常非线性控制方程来解决的。结果表明，在支承圆盘半径一定的情况下，液柱高度对动力学有很大影响。除了与不稳定开始的临界阈值(这使得Marangoni流具有时间周期性)的预期联系外，这个几何参数还可以对浮现的波形产生重大影响，从而对粒子结构的拓扑结构产生重大影响。对于浅液桥，脉动流是首选的对流方式，而对于高浮柱，主要结果表现为旋转流体动力扰动。在前一种情况下，粒子在由粒子耗竭区域内部限定的圆形扇区中自组织，而在后一种情况下，粒子被迫以螺旋状结构积累。其中一些粒子吸引子的性质在早期关于普朗特数值较小的流体的研究中很少观察到。
Systems of solid particles in suspension driven by a time-periodic flow tend to create structures in the carrier fluid that are reminiscent of highly regular geometrical items. Within such a line of inquiry, the present study provides numerical results in support of the space experiments JEREMI (Japanese and European Research Experiment on Marangoni flow Instabilities) planned for execution onboard the International Space Station. The problem is tackled by solving the unsteady non-linear governing equations for the same conditions that will be established in space (microgravity, 5 cSt silicone oil and different aspect ratios of the liquid bridge). The results reveal that for a fixed supporting disk radius, the dynamics are deeply influenced by the height of the liquid column. In addition to its expected link with the critical threshold for the onset of instability (which makes Marangoni flow time-periodic), this geometrical parameter can have a significant impact on the emerging waveform and therefore the topology of particle structures. While for shallow liquid bridges, pulsating flows are the preferred mode of convection, for tall floating columns the dominant outcome is represented by rotating fluid-dynamic disturbance. In the former situation, particles self-organize in circular sectors bounded internally by regions of particle depletion, whereas in the latter case, particles are forced to accumulate in a spiral-like structure. The properties of some of these particle attractors have rarely been observed in earlier studies concerned with fluids characterized by smaller values of the Prandtl number.