Numerical investigation of bubble breakup in a four‐branched microchannel based on non‐Newtonian pseudoplastic fluid

Bubble breakup in a four‐branched microchannel with carboxymethyl cellulose (CMC) solution was investigated by an improved coupled level set and volume of fluid (CLSVOF) method based on consideration of the rheological characteristic of the fluid. The validity of the numerical approach was satisfactorily verified by comparing with the experimental results. The regime and pattern of bubble breakup were evaluated by analyzing the evolution of bubble morphology. The effects of gas velocity, solution concentration, and subchannel width on daughter bubble length were examined, respectively. The results indicate that three split regimes at the branch comprising expansion, squeezing, and pinch‐off stage and three flow patterns including long slug, short slug, and bubble flows can be observed. Daughter bubble length increases with the gas velocity but decreases with the solution concentration. Particularly, the bubble length in the subchannel near the symmetry axis of main channel is always greater than that in the channel far from the axis. However, as the former channel shrinks, the bubble length in it will rapidly drop while the length in latter channel increases significantly. Finally, a scaling law to predict the daughter bubble length in two‐distanced channel is developed and agrees with the numerical results under present conditions.