Snap-off of gas bubbles in smoothly constricted noncircular capillaries

TLDR: In this article, a corner flow hydrodynamic theory is outlined for the time to snap-off of a gas bubble moving through a smoothly constricted noncircular capillary as a function of the pore geometry and the capillary number, Ca.

Abstract: A corner flow hydrodynamic theory is outlined for the time to snap-off of a gas bubble moving through a smoothly constricted noncircular capillary as a function of the pore geometry and the capillary number, Ca. Above a transition capillary number the time to snap-off is independent of Ca, while below it the time to snap-off is inversely proportional to the capillary number. Thin films of liquid deposited along the capillary walls are shown to play a minor role; they are accordingly neglected in the analysis. The proposed theory is compared to new experimental results for snap-off in two constricted square capillaries (dimensionless constriction radii of 0.3 and 0.5) over a range of capillary numbers (10/sup -5/ to 10/sup -3/), wetting-liquid viscosities (1.0 to 8.5 mPa . s), and surfactant types. Good agreement is found between theory and experiment.