Dynamics of Bubble Rising in Extremely High and Low Viscous Fluids

Bubble dynamics is a captivating field of study due to its complexity and wide-ranging applications. The present research focuses on bubble behavior in fluids with very high and low viscosities. Our study also focuses on understanding the effect of gas flow rate and needle diameter on bubble size. This research is essential because of scientific disagreement in this area, and our revisit adds new findings to the problem. We perform experiments in liquids with extreme viscosity differences using needles ranging from 0.84 mm to 1.54 mm and gas flow rates from 5 ml/min to 80 ml/min. In low-viscosity fluid, bubble necking time is constant with the flow rate, and secondary necking leads to daughter bubble formation. In high-viscosity fluid, bubble formation and rising differ, with smaller bubbles sliding over larger ones and merging symmetrically along their axis. The symmetry of contact decides sliding or coalescence. We also noticed that bubbles formed pairs (doublets) when the gas flow rate decreased with increasing needle size. The consecutive bubble diameter in both fluids is explored. The contrasting characteristics in low-viscosity environments (such as deionized water) and high-viscosity environments (like glycerol) highlight their respective monotonic and non-uniform flow behaviors.