UC Irvine

The deformation and breakup of droplets and bubbles in an immiscible carrier liquid in

micro-channels has been extensively investigated in the literature. In this study, we address

the case of bubbles in a T-junction at moderate Reynolds numbers, a problem that is

relevant for fluidics and emulsion processing applications. The main features include complex

oscillating transients, recirculation stabilization, and bubble stabilization against breakup.

In particular, very elongated bubble shapes are observed, which would be unstable in the

unbounded case and can be explained in terms of wall-induced distortion of the flow field. We

show that wall effects can be exploited to obtain nearly mono-disperse emulsions in confined

flows. Surface tension also plays an important role on the breakup of the dispersed phase.

Different bubble sizes can be obtained depending on the Capillary number as well as the

bubble initial size. A mechanism for finding the non-breakup and breakup regions depending

on bubble size is determined. This mechanism is determined with different initial flow rates

of the carrier flow. The non-breakup regime allows for the bubble to remain attached to the

bottom wall of the T-junction. In the breakup regime, the elongation of the bubble results

in a significant delay for breakup, allowing for the study of the breakup time and location.

Results are presented for different Ca and Re numbers.