Study on the Kinetic Characteristics of Microbubbles in Cross-Shaped Flow Focusing Microchannels

To study the mechanism of microbubbles generation in cross-shaped microchannels, numerical simulations of gas–liquid two-phase flow in microchannels are carried out in this paper using the volume of fluid method (VOF). By varying the two-phase flow rate, three different flow regimes were obtained, including dripping regime, slugging regime and threading regime, and the relationship between the two-phase flow rate and the flow state was plotted. Meanwhile, the phase interface, pressure and velocity of microbubbles in three different flow regimes were studied, and the evolution of the gas–liquid interface in microbubbles formation was analyzed. It is found that the microbubbles diameter decreases and the frequency increases as the viscosity of the continuous phase gradually increases. As the wall contact angle decreases, the adhesion of the liquid phase to the wall at the channel interaction increases and the microbubbles diameter increases. The increase in interfacial tension greatly increases the cohesion between molecules on the surface of the gas flow, making it difficult to achieve force equilibrium, which leads to a reduction in the shear stress required to dominate the interface to break the tip of the gas flow and slower bubbles formation, resulting in a larger microbubbles diameter.