Systematic Study on the Coalescence and Breakup Behaviors of Multiple Parallel Bubbles Rising in Power-law Fluid

Abstract

The coalescence and breakup behaviors of multiple parallel bubbles rising in power-law non-Newtonian fluid were investigated numerically by Volume of Fluid (VOF) method. The effects of the number of bubbles, bubble diameter, bubble interval, and flow index of power-law fluid on bubble coalescence and breakup were studied systematically. The dimensionless critical horizontal intervals of bubble coalescence for two, three, and four bubbles with different diameters were attained respectively by simulation under different flow indexes of power-law fluid. A quantitative criterion was developed to compute the critical bubble interval for bubble coalescence based on the critical approach velocity theory. Dramatic deformations of bubbles were found during the coalescence processes. Two different bubble coalescence and breakup behaviors were found and illustrated: (I) all bubbles coalesce into one big bubble; (II) coalescence of partial bubbles among multiple bubbles. For two or three parallel bubbles, only regime...