Motion and coalescense of gas bubbles in non-Newtonian polymer solutions

Abstract

In this paper, we report new results of an experimental study concerning the motion and coalescense of bubbles in viscoelastic polymer solutions. In particular, the shapes and velocity-volume characteristics of air nitrogen and carbon dioxide bubbles have been examined in solutions of polyacrylamide in 50/50 glycerine/water mixtures under a wide range of conditions. Furthermore, the possible effects of surface-active agents and of the aging characteristics of polymer solutions were also explored. Under no conditions did we observe an abrupt discontinuity in bubble velocity-volume data, and the fluid viscoelasticity is known to exert a significant influence in governing the shapes of bubbles moving in viscoelastic media. Finally, the coalescence of two bubbles simultaneously released from different orifices was studied in terms of the volume of one bubble required to achieve coalescence with a second bubble of fixed volume at predetermined heights above the orifices. Coalescence was studied with different polymer solutions for air, N₂ and CO₂ for a range of (initial) orifice separations. It is shown that the fluid viscoelasticity influences the coalescence via the shapes and wake characteristics of bubbles.