Ascending motion of bottom-blown bubbles in vertical channels

Abstract The gas-liquid two-phase flow is widely applied in engineering. Studying the bubble movement in the liquid phase is valuable for achieving efficient operation of relevant reactors. In this study, the ascending morphology of single-pore bubbles and double-pore bubbles in liquids was photographed by building a visualization experimental setup. Together with MATLAB, the effects of different variables on the ascending of bottom-blown bubbles were analyzed. Experimental results showed the bubble departure diameter was enlarged with the increase of pore inner diameter. At larger pore inner diameter, the bubble orbits were more disorderly, and the ultimate bubble velocity was smaller. At larger gas flow rate, the orbit of single bubbles was closer to a straight line, and the disturbance of double bubbles was intensified, leading to coalescence. The ultimate bubble velocity in water was accelerated with the increase of gas flow rate, and when the number of pores changed, the flow rate was more influential than the pore inner diameter on the ultimate bubble velocity. The centroid orbits of single bubbles were not significantly different between the two liquid-phase conditions, but the swinging amplitude of double bubbles in water was smaller than that in the 0.75% NaCl solution. The horizontal velocities were not significantly different, but the first velocity and ultimate velocity of bubbles at the vertical level in the 0.75% NaCl solution were both larger than those in water. These findings offer basic data for research on bubble strengthening and blending effects in vertical channels.