Two-phase flow and morphology of the gas–liquid interface for bubbles or droplets in different microchannels

Abstract

Two-phase interface fluid, bubble or droplet, has shown broad application potential in oil and gas field development, contaminated soil remediation, and medical treatment. These applications are particularly concerned about the flow characteristics of the two-phase fluid in different channels. Herein, we summarize and analyze the research progress in the flow of bubbles (or droplets) in different channels, mainly including simple, Y-junction/T-junction, and obstructed microchannels. At present, there is no systematic theory about the structure and mechanical evolution of the two-phase interface fluid, and therefore, the comprehensive study is still insufficient. Especially, current studies on the breakup of the two-phase interface in bifurcated channels mainly focus on a few of specific perspectives and a general conclusion is not achieved. In addition, to systematically verify the mechanism of bubble (or droplet) breakup, extensive studies on the three-dimensional physical model of bubbles (or droplets) are needed. Furthermore, we have also sorted out the involved influencing factors, as well as the prediction models for bubble (or droplet) breakup and retention in different channels, and in the end, we provide suggestions for the potential research and development of the two-phase interface fluid.

Equilibrium shape of a bubble in a liquid-filled horizontal capillary

“…A circular cross-section of the capillary results in approximately cylindrical bubble shapes (Atasi et al, 2018;Zhao et al, 2018), with the formation of a thin liquid film separating the bubble from the capillary wall (Atasi et al, 2018). The variation in width h of this film as a function of bubble velocity has been widely studied and various empirical equations have been proposed (Chen et al, 2023), in particular for elongated bubbles (Atasi et al, 2017;Danov et al, 2021;Jones et al, 2021;Moran et al, 2021). Such work dates back to Taylor (Taylor, 1960), who showed that the ratio h/R c (where R c is the channel radius) asymptotes to 1/3 for Ca → 2.…”

“…Here Ca is the dimensionless capillary number, Ca = μv b /σ, where μ is the viscosity of the liquid, v b is the bubble velocity, and σ is the surface tension of the gas-liquid interface. Subsequently, more detailed descriptions of the shape of the bubble, and thus the local thickness of the liquid film surrounding it have been obtained, together with respective scaling relations (Atasi et al, 2018;Chen et al, 2023).…”