Bubble formation in T-junctions within parallelized microchannels: Effect of viscoelasticity

Abstract

The effects of viscoelasticity on formation process, size and generation frequency of bubbles in T-junctions within symmetrical parallelized microchannels are investigated by a high-speed camera system. Air and polyethylene oxide (PEO)-glycerol solutions with 0.3% SDS are used as the dispersed and continuous phases, respectively. Three flow patterns are observed including slug, bubbly and beads-on-string flows. The evolution of the gaseous neck during bubble formation under various flow patterns, flow rate ratios of liquid and gas, and molecular weights of PEO is studied based on the distribution of elastic stress in the microchannel. The results reveal that the increase of the Weissenberg number is beneficial to the bubble breakup, and the uniformity of bubble size in the parallelized microchannels is better with higher flow rate ratios of liquid and gas. Finally, the semi-empirical formulas for the size and generation frequency of bubbles in the parallelized microchannels are established.