Croccolo Fabrizio, Brogioli Doriano, Vailati Alberto
Laboratoire des Fluides Complexes et leurs Réservoirs (LFCR), IPRA, UMR5150 E2S-Univ Pau & Pays Adour, CNRS, TOTAL, 64600 Anglet, France.
Universität Bremen, Energiespeicher-und Energiewandlersysteme, Bibliothekstraße 1, 28359 Bremen, Germany.
Rev Sci Instrum. 2019 Aug;90(8):085109. doi: 10.1063/1.5112778.
We describe a flowing-junction cell with cylindrical symmetry suitable to investigate fluctuations and pattern formation at the diffusing interface between two miscible phases of a liquid mixture. The continuous outflow of the remixed fluid through a thin slit located at the midheight of the sample allows the preparation of an initially sharp interface. The system can be used in both gravity-stable and unstable conditions. In the stable case, the denser liquid is on the bottom of the cell and mass diffusion is the only active process for remixing the two liquids. Once the flow is stopped, one can investigate nonequilibrium fluctuations during free-diffusion in a binary mixture or double diffusive instabilities in multicomponent mixtures. Two horizontal transparent windows allow vertical mapping of the fluid flow by using shadowgraphy. In the unstable condition, with the denser fluid on top, stopping the radial flow at the interface gives rise to a Rayleigh-Taylor instability, which drives the denser liquid toward the bottom of the cell. The fact that the cell can maintain the system in the unstable condition shows that it is suitable to perform experiments under microgravity conditions. With respect to other free-diffusion cells, the proposed configuration has the advantage that the interface is extremely stable and flat, and that the experiments can be repeated by just flowing the cell with fresh liquids.
我们描述了一种具有圆柱对称性的流动结电池，适用于研究液体混合物两个互溶相之间扩散界面处的涨落和图案形成。通过位于样品中部高度的细缝连续流出重新混合的流体，可以制备出初始尖锐的界面。该系统可在重力稳定和不稳定条件下使用。在稳定情况下，密度较大的液体位于电池底部，质量扩散是使两种液体重新混合的唯一活跃过程。一旦流动停止，就可以研究二元混合物自由扩散过程中的非平衡涨落或多组分混合物中的双扩散不稳定性。两个水平透明窗口允许通过阴影成像对流体流动进行垂直映射。在不稳定条件下，密度较大的流体在顶部，停止界面处的径向流动会产生瑞利 - 泰勒不稳定性，从而驱使密度较大的液体流向电池底部。该电池能够将系统维持在不稳定状态这一事实表明，它适用于在微重力条件下进行实验。与其他自由扩散电池相比，所提出的配置具有界面极其稳定和平坦的优点，并且只需用新鲜液体使电池流动就可以重复实验。
