Dimple drainage before the coalescence of a droplet deposited on a smooth substrate
Dimple drainage before the coalescence of a droplet deposited on a smooth substrate
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沉积在光滑基材上的液滴聚结之前的凹坑排水
DOI：
10.1073/pnas.2007857117
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
C. Josserand
中科院分区：
文献类型：
--
作者：
L. Duchemin;C. Josserand
意义当毫米级的水滴落在光滑的表面上时，无论是液体还是固体，分隔表面和水滴的空气层的缓慢重力排放会导致下面被困住一个薄薄的气泡。在这项工作中，我们从理论和数值计算两个方面研究了气泡在固体和液体膜上的排水动力学。我们展示并解释了如何在薄的液膜上比在固体表面上更快地在聚结之前进行这种动力学。薄薄的液体或气体薄膜在自然界中无处不在，从泡沫到自由表面的亚毫米气泡，它们的破裂留下了许多小液滴和气泡。然而，导致这些电影破灭的机制仍存在争议。因此，本研究的目的是了解毫米级液滴与光滑的固体或液体薄膜之间的重力挤压薄空气膜的排水动力学。通过求解耦合的润滑方程并分析固体和液膜情况下的主导项，我们解释了为什么液膜情况下的排水速度快得多，这通常导致聚结时间较短，正如最近的实验所观察到的那样。
Significance When a millimetric droplet is laying on a smooth surface, either liquid or solid, the slow gravity drainage of the air layer separating the surface from the drop leads to the entrapment of a thin bubble underneath. In this work, we investigate theoretically, and through numerical computations, the bubble-drainage dynamics on a solid and a liquid film. We show and explain how this dynamics before coalescence is much faster on a thin liquid film than on a solid surface. Thin liquid or gas films are everywhere in nature, from foams to submillimetric bubbles at a free surface, and their rupture leaves a collection of small drops and bubbles. However, the mechanisms at play responsible for the bursting of these films is still in debate. The present study thus aims at understanding the drainage dynamics of the thin air film squeezed by gravity between a millimetric droplet and a smooth solid or a liquid thin film. Solving coupled lubrication equations and analyzing the dominant terms in the solid- and liquid-film cases, we explain why the drainage is much faster in the liquid-film case, leading often to a shorter coalescence time, as observed in recent experiments.