Y型微通道中两相界面特性变化分析

Numerical Analysis on Two-phase Flow Characteristics at Convection Microfluidic Y-junctions

利用追踪运动界面的两相流模型数值研究对流Y型微通道中两相界面形貌变化特性。发现对流Y型微通道Y型角度、连续相毛细数、两相流量对液滴生成时间、速度、大小有重要影响。其中连续相毛细数与Y型角度越小,所生成的液滴体积越大,而随着分散相与连续相流量比例的增大,其对液滴体积的影响变小,但流量比不能无限增大或减小,当比值大于0.5或小于0.05时,此时分散相只能以液柱或液丝的形式出现,无法产生液滴;当分散相流量越大,相应液滴的生成速度也几乎成比例增大,且分散相流量的变化对液滴长度的演变过程有更大的影响。此外随Y型角度的增加,液滴在形成过程中,填充时间变长,缩颈时间变短,液滴脱离机理主要是因为来自连续相正应力的作用。

Numerical simulation on two-phase flow characteristics at convection microfluidic Y-junctions based on the two-phase flow interface tracking method. It is found that the Y-angle of the microfiuidic Y-junctions, capillary number of continuous phase, and the flux of two phases have a great infuence on droplet generation time, rate and size. The decreasing of continuous phase capillary number and Y-angle results in the increasing of the droplet volume. At the same time, with the increasing of flux ratio of the dispersed phase and continuous phase, the influence on the droplet volume is becoming smaller. But the flow flux ratio cannot infinite increase or decrease. Because the dispersed phase can only takes the form of liquid colunm or silk and it unable to generate the droplet when the ratio is greater than 0.5 or no more than 0.05. When the dispersed phase flux is increasing, the corresponding droplet formation rate is almost proportional increasing; the influence of the dispersed phase flow on the length of the droplets evolution is greater than the continuous phase. In addition, in the formation process of droplet, the filling time becomes longer and the necking time becomes shorter with the increasing of the Y-angle. The droplet detachment mechanism is mainly under the effect of normal stress of the continuous phase.