New insights into the pressure during the merged droplet formation in the squeezing time

• Published in: Chemical engineering research & design 2019-05, Vol.145, p.213-225
• Main Authors: Han, Wenbo, Chen, Xueye
• Format: Article
• Language: English
• Subjects: Capillary number; Capillary pressure; Compressing; Computer simulation; Continuous flow; Droplets; Flow velocity; Level-set simulation; Merged droplet formation; Microchannels; Numerical analysis; Pressure; Pressure drop; Squeezing; Strain rate; Studies; Surface tension; Variations; Viscosity
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2019.03.002

[Display omitted] •Simulation of the merged droplet formation in the double T-junction was performed.•It is shown that pressure fluctuation period is the same as the generation period.•New insights into the pressure during the merged droplet formation are reported. In this paper, a three-dimensional numerical simulation of the merged droplet formation (MDF) in the double T-junction microchannel was performed to investigate the effects of the flow rate of the continuous phase, continuous viscosity and the interfacial tension on the pressure by the level-set method. We divide the droplet formation process into three stages, namely filling, blocking and breakup. We define the time to generate a droplet as the droplet generation period. The characteristic length L/W (L is the length of the droplet, and W is the width of the main channel) decreases as the capillary number increases. The pressure (PA) at a special position at the junction of the two phases occurs periodically during the droplet formation process, which directly and precisely reflects the mechanism of the MDF in the microchannel. Therefore, we define the time during the pressure fluctuates periodically as the pressure fluctuation period. New insights into the pressure during the MDF in the squeezing time are reported. The results show that the pressure fluctuation period and pressure drop period are the same as the droplet generation period. When the continuous flow rate and viscosity increase, the peak and valley values of PA and the pressure drop increase, and the time of the pressure cycle decreases. However, when the interfacial tension increases, the peak and theperiod increase and the valley decreases.