Hydrodynamic Interaction And Coalescent Motion Of Air-bubbles Floating In Liquid Flow
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T. Kumagai, S. Yoshiyasu, K. Yokota & M. Muraoka
A new theoretical method is proposed to estimate the hydrodynamic interaction among air-bubbles in a viscous liquid at low Reynolds numbers in relation to multi-phase flow in industrial applications. This method is a superposition method of Oseen’s flow fields around cach air-bubble, of which the shape is deformable during its motion. The experiment is carried out using a glycerol tank and high-speed video-cameras with 10000 frames/s. Equal-sized air-bubbles located vertically with the same spacings at the initial time showed an interesting motion to make pairs of air-bubbles from the preceding two air-bubbles successively in turn. In these pairs of air-bubbles the following air-bubble approached the preceding air-bubble. During the approaching motion the shape of the preceding air-bubble became oblate, while the following air-bubble became prolate. Then the two air-bubbles contacted and coalesced finally. During the coalescent motion of two air-bubbles there were recognized an occurrence of several micro-bubbles. The numerical results predicted by using the superposition method of Oseen’s flow field agree well with the experimental results.