Volume-of-fluid simulations in microfluidic T-junction devices: Influence of viscosity ratio on droplet size
Volume-of-fluid simulations in microfluidic T-junction devices: Influence of viscosity ratio on droplet size
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DOI：
10.1063/1.4978801
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发表时间：
2017-03-01
影响因子：
4.6
通讯作者：
Vanapalli, Siva A.
中科院分区：
文献类型：
--
作者：
Nekouei, Mehdi;Vanapalli, Siva A.
采用流体体积法对微流控T型连接器件中牛顿流体的液滴形成过程进行了三维数值模拟。为了评估VOF方法的性能，我们研究了液滴形成的制度，并确定液滴尺寸作为系统参数的函数。模拟结果与文献中的四组实验数据的比较显示出良好的一致性，验证了VOF方法。由于缺乏足够的研究来调查粘度比（λ）对所产生的液滴尺寸的影响，我们绘制了液滴体积对毛细管数（0.001 < Ca < 0.5）和粘度比（0.01 <λ < 15）的依赖性。我们发现，对于所有的粘度比调查，液滴的大小随着毛细管数的增加而减小。然而，随着毛细管数的液滴尺寸的减小对于λ 1更强< 1 than for lambda >。此外，我们发现，在给定的毛细管数，液滴的大小没有明显的变化时，λ < 1，而它增加时，λ> 1。我们开发了一个分析模型，用于预测液滴的大小，其中包括一个粘度依赖的分散相的破碎时间。这种改进的模型成功地预测了模拟中观察到的粘度比的影响。从这项研究的结果是有用的芯片上的实验室技术的设计和制造的微流控乳液，有必要知道系统参数如何影响液滴的大小。由AIP出版社出版。
We used volume-of-fluid (VOF) method to perform three-dimensional numerical simulations of droplet formation of Newtonian fluids in microfluidic T-junction devices. To evaluate the performance of the VOF method we examined the regimes of drop formation and determined droplet size as a function of system parameters. Comparison of the simulation results with four sets of experimental data from the literature showed good agreement, validating the VOF method. Motivated by the lack of adequate studies investigating the influence of viscosity ratio (lambda) on the generated droplet size, we mapped the dependence of drop volume on capillary number (0.001 < Ca < 0.5) and viscosity ratio (0.01 < lambda < 15). We find that for all viscosity ratios investigated, the droplet size decreases with increase in the capillary number. However, the reduction in the droplet size with the capillary number is stronger for lambda < 1 than for lambda > 1. In addition, we find that at a given capillary number, the size of droplets does not vary appreciably when lambda < 1, while it increases when lambda > 1. We develop an analytical model for predicting the droplet size that includes a viscosity-dependent breakup time for the dispersed phase. This improved model successfully predicts the effects of the viscosity ratio observed in simulations. Results from this study are useful for the design of lab-on-chip technologies and manufacture of microfluidic emulsions, where there is a need to know how system parameters influence the droplet size. Published by AIP Publishing.