Microcavity-Enabled Local Oscillation Of Taylor Bubbles In A Microchannel

Interphase mass transport is important for many industrial applications ranging from multiphase reaction and separation but remains a great challenge in maximizing the interface area and mass-transfer flux. In this work, a periodical oscillation of Taylor bubbles is demonstrated to enhance interface transport by arranging gas microcavities on the walls of a rectangular microchannel. Bubble oscillation is characterized as the expansion and contraction of the bubble tail near the gas microcavity. Microscope visualization results show that the oscillation amplitude increases with a decrease of cavity width, while it decreases with an increase of capillary number. This is attributed to the increased hydrodynamic resistance in the liquid film between bubble surface and gas microcavity. The evolution of slip velocity at the gas microcavity interface is numerically investigated to explain the interaction between dynamic pressure and Laplace pressure, where bubble velocity fluctuation occurs. A bubble oscillation map is proposed to offer insight into the role of the gas microcavity, providing a quantitative basis to optimize the surface design and operating conditions.