Numerical investigation of gas-liquid and liquid-liquid Taylor flow through a circular microchannel with a sudden expansion

This paper investigates a CFD-based analysis for gas-liquid and liquid-liquid Taylor flows through a circular axisymmetric microchannel with a sudden enlargement. A series of simulations are conducted by exploring the influence of different superficial velocity ratios, apparent viscosities, and channel expansion on the hydrodynamics of slug flow. A concentric junction introduces dispersed airflow into a continuous flow of water for gas-liquid flow, and the junction introduces dispersed water into a continuous flow of dodecane for liquid-liquid flow. The air-bubble and water-slug evolution processes, slug breakup, and slug expansion are investigated. In all cases, the lengths of air bubbles and water slugs increase with increasing superficial velocity ratio, particularly before the expansion. For gas-liquid flow, the apparent viscosity ratio causes a fluctuating interface over the uniform film region. However, the water slug length is shorter and the film region is slightly thicker in liquid-liquid compared to gas-liquid flow. The numerical analysis developed in this paper is in good agreement with the existing correlations and experimental data in the literature.