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 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.