Abstract
For clarifying detail structure of bubbly flows which have multi-scale structure, it is necessary to understand bubble-bubble interaction phenomena. Some theoretical models of interaction between two spherical bubbles located in-line rising in a viscous liquid have been proposed, however experimental verifications are insufficient. In this study, we observed motion of a pair of spherical bubbles initially located in-line rising in quiescent ultrapure water or aqueous surfactant solutions. The bubble Reynolds number is ranged from 50 to 300. The results indicate that the slight difference between bubbles radius greatly affects the relative motion. When radius of the trailing bubble is larger than that of the reading bubble, the trailing bubble approaches to the reading bubble. Otherwise the trailing bubble separates from the reading bubble. Also the lift force acts on the trailing bubble when bubbles located in-line, and bubbles attract in the transverse direction when bubbles located about side by side.
