Velocity Evolution for the Coalescence of Two In-Line Bubbles Rising in Non-Newtonian Fluids

Abstract

This study experimentally investigates velocity evolution for the coalescence of two in-line bubbles rising in non-Newtonian fluids by using a high speed camera. Due to the wake of the leading bubble and the shear-thinning effect of non-Newtonian fluids, the following bubble is accelerated to approach the leading bubble, leading to the coalescence of the two bubbles. Based on the Newton’s second law and Schlichting’s wake theory, a theoretical model was developed to estimate the instantaneous rising velocity of the following bubble in the coalescence process of the two bubbles. The predicted values by the present model showed a good agreement with the experimental data.