Dynamics of bubble formation in yield stress fluids in parallelized microchannels

The bubble formation in yield stress fluids in parallelized microchannels is investigated experimentally. Nitrogen and Carbopol gel are used as the dispersed and continuous phases, respectively. Due to the feed-back effect of the downstream microchannels, the uniformity and stability of bubble formation strongly depends on the properties of gels and operating conditions. The effect of yield stress on the interface evo-lution during bubble formation is investigated under different mass factions of Carbopol (0.2 %, 0.13 %, 0.05 %) and flow rates of gas (0.1-400 mL center dot min (1)) and liquid (0.03-0.2 mL center dot min (1)). The activation rate of parallel microchannels for bubble production increases with the decrease in the concentrations of Carbopol. The increase of liquid flow rate and the decrease of gas flow rate benefit the uniformity of bub-ble formation frequency. However, under the double-channel bubble-generation flow pattern, reducing the liquid flow rate significantly improves the stability of bubble formation. (c) 2022 Elsevier Ltd. All rights reserved.