Coalescence and rising behavior of co-axial and lateral bubbles in viscous fluid: a CFD study

Abstract

The coalescence and rising behavior of co-axial and lateral bubbles play a valuable role in industrial bubble column which operates at non-ambient conditions. The volume of fluid with the continuum surface force (VOF-CSF) model is used for the present study. Three main case studies, namely under ambient and aqueous condition, μ* = σ* = 1, under reduced viscosity, μ* = 0.1, and surface tension, σ* = 0.1, are investigated and compared using two co-axial bubbles and three lateral bubble rise configuration models. The latter two cases represent operating conditions at above the ambient temperature or pressure. Prior to investigating the main cases, the model is validated with the experimental data from the literature for a single bubble and two lateral bubble coalescence. It is found that reducing viscosity and surface tension has a significant effect on the co-axial bubbles (or a pair of bubbles rising in a vertical line) and three lateral bubble growth and coalescence characteristics, as compared to ambient condition.