A Model of Gas Bubble Growth by Comsol Multiphysics

We use Comsol Multiphysics to model a gas bubble expansion in a viscous liquid initially at rest, a very common system for lightweight foamed materials from metal production and polymer processing. The aim of the present work is to develop a first computational model for the growth of gas bubbles under simpler conditions, modeling both the gas and liquid flow and to verify its validity by comparing the numerical results with existing analytical solutions. The two dimensional isothermal model developed in Comsol Multiphysics considers a gas bubble growing due to a pressure difference with a surrounding Newtonian liquid. Surface tension effects on the gas-liquid interface are considered. The model equations are solved on a fixed grid, built both in the gas than in the liquid region. In order to capture the front between the two fluids we exploit the capability of the level set method. The numerical results of the computational model compare well with analytical solutions from theory and obtained for a few simple cases. This first computational work is a basis for considering successive more realistic foam expansions.