Bubble Dynamics in Multiphase Flow in a T-junction at Moderate Reynolds Numbers

The deformation and breakup of droplets and bubbles in an immiscible carrier liquid inmicro-channels has been extensively investigated in the literature. In this study, we addressthe case of bubbles in a T-junction at moderate Reynolds numbers, a problem that isrelevant for fluidics and emulsion processing applications. The main features include complexoscillating transients, recirculation stabilization, and bubble stabilization against breakup.In particular, very elongated bubble shapes are observed, which would be unstable in theunbounded case and can be explained in terms of wall-induced distortion of the flow field. Weshow that wall effects can be exploited to obtain nearly mono-disperse emulsions in confinedflows. 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 thebubble initial size. A mechanism for finding the non-breakup and breakup regions dependingon bubble size is determined. This mechanism is determined with different initial flow ratesof the carrier flow. The non-breakup regime allows for the bubble to remain attached to thebottom wall of the T-junction. In the breakup regime, the elongation of the bubble resultsin a significant delay for breakup, allowing for the study of the breakup time and location.Results are presented for different Ca and Re numbers.