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.

中文翻译：

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突然膨胀的圆形微通道中气-液和液-液泰勒流的数值研究

本文研究了基于 CFD 的气液和液液泰勒流过突然扩大的圆形轴对称微通道的分析。通过探索不同的表观速度比、表观粘度和通道扩展对段塞流流体动力学的影响，进行了一系列模拟。同心接头将分散的气流引入连续的水流中以实现气-液流动，而该接头将分散的水引入连续的十二烷流中以实现液-液流动。研究了气泡和水段塞演化过程、段塞破裂和段塞膨胀。在所有情况下，气泡和水段塞的长度随着表观速度比的增加而增加，特别是在膨胀之前。对于气液流动，表观粘度比导致均匀薄膜区域上的界面波动。然而，与气-液流动相比，液-液中的水段塞长度较短且膜区域稍厚。本文开发的数值分析与文献中现有的相关性和实验数据非常吻合。