ANALYSIS OF DIFFUSION-INDUCED BUBBLE-GROWTH IN VISCOELASTIC LIQUIDS

Transport models of diffusion-induced bubble growth in viscoelastic li quids are developed and evaluated. A rigorous model is formulated that can be used to describe bubble growth or collapse in a non-linear vis coelastic fluid, and takes into account convective and diffusive mass transport as well as surface tension and inertial effects. Predictions for bubble growth dynamics demonstrating the importance of fluid elas ticity are presented. These predictions indicate that for diffusion-in duced bubble growth in viscoelastic liquids, the lower bound for growt h rate is given by growth in a Newtonian fluid and the upper bound by diffusion-controlled growth. The influence of non-linear fluid rheolog y on bubble growth dynamics is examined and found to be relatively min or in comparison to fluid elasticity. It is shown how previously publi shed models employing various approximations can be derived from the r igorous model. Comparisons of predicted bubble growth dynamics from th e rigorous and approximate models are used to establish the ranges of applicability for two commonly-used approximations. These comparisons indicate that models using a thin boundary layer approximation have a rather limited range of applicability. An analysis of published experi mental bubble growth data is also carried out using appropriate transp ort models. (C) 1998 Elsevier Science B.V.