Bubble breakup dynamics in a semicircular pore throat microchannel

This work investigates the dynamics of gas–liquid interface breakup and bubble formation in oil microchannels (with oil as the continuous phase). A high-speed camera was utilized to examine the breakup behavior of bubbles in a microchannel with two semi-cylinders (simulating semicircular pore throats). The deformation behavior of bubbles is classified into three stages for obstructed breakup and non-breakup, and four stages for coalescence after breakup, based on the change process of the minimum neck width with time. A power-law relationship is observed between the minimum neck width and time for each stage. The impact of pre-factors such as the fluid flow rate and capillary number (Ca, a dimensionless parameter reflecting the ratio of viscous forces to interfacial tension forces of the continuous phase) on the breakup dynamics is discussed. The micro-particle image velocimetry is used to investigate the velocity field in the liquid phase surrounding the gaseous thread to understand the mechanism of bubble breakup with obstruction. A scaling law is proposed to describe the size of bubbles generated in liquid at microchannels. The study reveals the importance of the physical properties of the continuous phase in bubble deformation: the continuous phase's viscosity (μc) and interfacial tension (σ) directly regulate the squeezing pressure, shear stress, and extensional stress acting on bubbles during their passage through the pore throat. These forces determine the duration and intensity of each deformation stage, ultimately governing whether bubbles undergo obstructed breakup, post-breakup coalescence, or non-breakup. These findings provide a foundation for understanding bubble dynamics in porous media, which is critical for enhanced oil recovery applications.