Dynamics of two coaxially rising gas bubbles

In this study, the coalescence dynamics of two unequal sized vertically inline bubbles rising in a liquid column have been investigated using the coupled level-set and volume-of-fluid (CLSVOF) method. A wide range of bubble radius ratios of trailing bubble and leading bubble ( 0.25 ≤ R ≤ 2.0) and se...

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Bibliographic Details
Published in:Physics of fluids (1994) 2021-05, Vol.33 (5)
Main Authors: Kumar, Adarsh, Ray, Bahni, Biswas, Gautam
Format: Article
Language:English
Subjects:
Bubbles
Coalescing
Entrapment
Fluid dynamics
Physics
Vortex rings
Wakes
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Summary:In this study, the coalescence dynamics of two unequal sized vertically inline bubbles rising in a liquid column have been investigated using the coupled level-set and volume-of-fluid (CLSVOF) method. A wide range of bubble radius ratios of trailing bubble and leading bubble ( 0.25 ≤ R ≤ 2.0) and separation distances between the bubbles ( 2.5 ≤ S ≤ 3.5) have been deployed to investigate the evolution of the bubble wakes and bubble shapes. It is discovered that the coalescence time increases with R, the maxima being around 0.75 ≤ R ≤ 1, and then it decreases. With the increase in S, the coalescence time gradually increases. The existence of a pair of counter-rotating vortex rings has been observed between the bubbles, which are seen to accelerate the bubble coalescence process. For the present range of R and S, we show a regime map with four distinct coalescence pathways: coalescence with liquid entrapment, coalescence without liquid entrapment, penetration of the leading bubble, and premature splitting of the trailing bubble.
ISSN:1070-6631
1089-7666
DOI:10.1063/5.0048595