SCI和EI收录∣中国化工学会会刊

• Fluid Dynamics and Transport Phenomena •

### Coalescence dynamics of two droplets of different viscosities in T-junction microchannel with a funnel-typed expansion chamber

Weixi Guo, Chunying Zhu, Taotao Fu, Youguang Ma

1. State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
• Received:2021-01-22 Revised:2021-03-19 Online:2021-12-02 Published:2021-10-28
• Contact: Chunying Zhu, Youguang Ma
• Supported by:
This work is supported by the National Natural Science Foundation of China (92034303, 91834303 and 21776200), and thanks for the aid of Program of Introducing Talents of Discipline to Universities (BP0618007).

### Coalescence dynamics of two droplets of different viscosities in T-junction microchannel with a funnel-typed expansion chamber

Weixi Guo, Chunying Zhu, Taotao Fu, Youguang Ma

1. State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
• 通讯作者: Chunying Zhu, Youguang Ma
• 基金资助:
This work is supported by the National Natural Science Foundation of China (92034303, 91834303 and 21776200), and thanks for the aid of Program of Introducing Talents of Discipline to Universities (BP0618007).

Abstract: The coalescence behavior of two droplets with different viscosities in the funnel-typed expansion chamber in T-junction microchannel was investigated experimentally and compared with droplet coalescence of the same viscosity. Four types of coalescence regimes were observed: contact non-coalescence, squeeze non-coalescence, two-droplet coalescence and pinch-off coalescence. For droplet coalescence of different viscosities, the operating range of non-coalescence becomes narrowed compared to the droplet coalescence of same viscosity, and it shrinks with increasing viscosity ratio η of two droplets, indicating that the difference in the viscosity of two droplets is conducive to coalescence, especially when 1<η<6. Furthermore, the influences of viscosity ratio and droplet size on the film drainage time (Tdr) and critical capillary number (Cac) were studied systematically. It was found that the film drainage time declined with the increase of average droplet size, which abided by power-law relation with the size difference and viscosity ratio of the two droplets: Tdr ~ (ld)0.25±0.04 and Tdr ~ (η)-0.1±0.02. For droplet coalescence of same viscosity, the relation of critical capillary number with two-phase viscosity ratio and dimensionless droplet size is Cac = 0.48λ0.26l-2.64, while for droplet coalescence of different viscosities, the scaling of critical capillary number with dimensionless average droplet size, dimensionless droplet size difference and viscosity ratio of two droplets is Cac = 0.11η-0.07ls-2.23ld0.16.