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Continuous formation of microbubbles during partial coalescence of bubbles from a submerged capillary nozzle
Author(s) -
Tang Jiguo,
Yu Shengzhi,
Sun Licheng,
Xie Guo,
Li Xiao
Publication year - 2020
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.16233
Subject(s) - microbubbles , nozzle , coalescence (physics) , capillary action , mechanics , bubble , materials science , liquid bubble , flow visualization , capillary number , radius , chemistry , flow (mathematics) , thermodynamics , composite material , physics , acoustics , ultrasound , computer security , astrobiology , computer science
Bubble formation from a downward‐pointing capillary nozzle was investigated in this study. The experiments were conducted at gas flow rate of 40–5,400 ml/h and inner nozzle radius of 0.030–0.255 mm. Experimental results show that microbubbles are formed continuously at moderate Weber number, which was not reported in pervious investigations with injecting gas through an upward‐pointing capillary nozzle. High‐speed visualization indicates that the formation of microbubbles arises from the convergence of the capillary waves induced by the partial coalescence of larger bubbles. A bubbling regime map is given to identify the critical conditions for the formation of microbubbles. In the present air‐water experiments, the generated microbubbles are 20–170 μm in diameter. From experimental data, a scaling law for microbubble size is proposed as a function of Weber and Bond numbers.