Author(s)

J. Hua, S. Quan & J. Nossen

Abstract

A Computational Fluid Dynamics (CFD) based front tracking algorithm is applied to investigate the rising behaviour of a single bubble in a vertical pipe with a stagnant or flowing viscous liquid. The ratio of the pipe diameter to the bubble equivalent diameter ( b D D / ) is varied within the range of 1.0∼10.0. The wall effects on the terminal bubble rising speed (U ) and shape are investigated under various flow conditions, which are characterised by the parameters Archimedes number ( Ar ), Bond number ( Bo ), and bulk liquid flow speed ( l U ). It is found that the terminal bubble rising speed (U ) relates to the bubble rising speed in an infinite domain ( ∞ U ) and the pipe diameter by the formula α ) / ( / ) ( D D U U U b ∝ − ∞ ∞ , where αis an exponent relating to the bubble deformability, and it is found to be in the range of 1.0∼0.7 in this study. In addition, the effects of flowing liquid on the terminal bubble rising speed and shape are also investigated for different sized pipes. It is demonstrated that the bubble rising behaviour is significantly affected by the flowing liquid in the pipe with a small diameter. Moreover, the detailed flow field around the bubble is presented to understand the physics of bubble rising behaviour in a vertical pipe under various flow conditions. Keywords: bubble rising, wall effect, front tracking method, Taylor bubble.

Keywords

bubble rising, wall effect, front tracking method, Taylor bubble