Plug flow of immiscible liquids with low viscosity ratio in serpentine microchannels

The paper aims to assess hydrodynamic features of liquid-liquid flows in serpentine microchannels to control mixing and mass transfer. Segmented or plug flow of the oil-water system in serpentine microchannels with different curvatures is studied. The novelty of the topic consists in the use of multiple bends of high curvature (width to curvature radius ratio beta = 1) in conjunction with the low viscosity ratio of phases (lambda = 0.001). Plug acceleration/deceleration in straight parts and bends depends on the channel curvature and leads to a drastic change in the plug length. Plug elongation is more pronounced for higher channel curvature and is found to be a linear function on the capillary number. Plug rupture is discovered in the microchannel with beta = 1. Flow structure in both the oil slugs and aqueous plugs is visualized using laser-induced fluorescence and particle tracking velocimetry techniques. Qualitatively different flow patterns in oil slugs are revealed depending on the bend curvature. In the aqueous plugs additional vortex appears due to curvature influence and intensifies for higher curvature. Optimal conditions for efficient mixing and mass transfer in the plug flow regime are stated.

Automated summary

The study focuses on the hydrodynamic features of liquid-liquid flows in serpentine microchannels to control mixing and mass transfer. Different curvatures of the microchannels lead to changes in plug acceleration/deceleration, plug length, and flow patterns in both oil slugs and aqueous plugs. Optimal conditions for efficient mixing and mass transfer in the plug flow regime are determined based on the research findings.