Mixing and internal dynamics of droplets impacting and coalescing on a solid surface
Mixing and internal dynamics of droplets impacting and coalescing on a solid surface
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DOI：
10.1103/physreve.88.023023
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发表时间：
2013-08-26
影响因子：
2.4
通讯作者：
Hutchings, I. M.
中科院分区：
文献类型：
--
作者：
Castrejon-Pita, J. R.;Kubiak, K. J.;Hutchings, I. M.
从横向分离和液滴速度两个方面对固壁液滴与撞击液滴的聚并与混合进行了实验和数值研究。两个液滴发生器用于产生不同颜色的液滴。两个高速成像系统被用来调查的影响和聚结的液滴的颜色从侧面的同时从下面的灰度视图。毫米大小的液滴与动态条件一起使用，基于雷诺数和韦伯数，与微流体和商业喷墨打印相关。前进和后退的静态接触角的实验测量被用来校准接触角滞后模型内的晶格玻尔兹曼框架，这是示出捕捉所观察到的动态定性和最终的液滴配置定量。我们的研究结果表明，没有检测到的混合过程中发生的影响和合并的相似大小的液滴，但当固着液滴是足够大的比冲击液滴涡环生成可以观察到。最后，我们展示了如何在基板上的润湿性梯度可以潜在地提高混合。
The coalescence and mixing of a sessile and an impacting liquid droplet on a solid surface are studied experimentally and numerically in terms of lateral separation and droplet speed. Two droplet generators are used to produce differently colored droplets. Two high-speed imaging systems are used to investigate the impact and coalescence of the droplets in color from a side view with a simultaneous gray-scale view from below. Millimeter-sized droplets were used with dynamical conditions, based on the Reynolds and Weber numbers, relevant to microfluidics and commercial inkjet printing. Experimental measurements of advancing and receding static contact angles are used to calibrate a contact angle hysteresis model within a lattice Boltzmann framework, which is shown to capture the observed dynamics qualitatively and the final droplet configuration quantitatively. Our results show that no detectable mixing occurs during impact and coalescence of similar-sized droplets, but when the sessile droplet is sufficiently larger than the impacting droplet vortex ring generation can be observed. Finally we show how a gradient of wettability on the substrate can potentially enhance mixing.