On the Motion of a Bubble through MicroChannel Contractions

摘要

We present the first transient pressure measurements and high-speed visualization of gas bubbles passing through liquid-filled microchannel contractions. We have studied contractions ranging from 100 to 500 μm in glass tubes of main diameter 2 mm and compared the experimental results with a recent model of quasi-stationary bubble motion. Transient pressure measurements, bubble deformations, and the influence of the bubble length on the so-called clogging pressure ΔP_c are shown to be in good agreement with the model, both in terms of maximum values and transient evolution. Some deviations from the model are also observed and possible reasons for this are investigated, such as contact line pinning, thin liquid film along the bubble and capillary instabilities. We also propose a criterion based on a modified capillary number to discriminate between two flow regimes: a quasi-stationary regime for low capillary number, and a viscosity-influenced regime for non-negligible capillary numbers.