Competitive growth and rising of bubbles in a yield stress fluid. Consequences on the macroscopic swelling of bitumen drums

• Published in: Journal of non-Newtonian fluid mechanics 2016-08, Vol.234, p.162-169
• Main Authors: Marchal, A., Vergnes, B., Poulesquen, A., Valette, R.
• Format: Article
• Language: English
• Subjects: Bubbles; Engineering Sciences; Kinetic model; Materials; Swelling; Yield stress
• ISSN: 0377-0257; 1873-2631
• DOI: 10.1016/j.jnnfm.2016.06.010

•We present a kinetic model for bubbles population nucleation, growth/collapse and migration due to buoyancy in a yield stress fluid matrix.•We study the influence of the yield-stress and nucleation type on the swelling of the system.•The yield stress plays an amplifying role on the swelling and induces delays in evacuation of bubbles by migration. The evolution kinetics of a bubble population driven by a uniform production of gas in a yield-stress fluid matrix is investigated in this paper. The context concerns the long time swelling of bitumen drums in which radioactive salts have been dispersed (salts suspensions in a bitumen matrix). Radioactivity generates uniform volume production of hydrogen by radiolysis of bitumen chains. Since the production rate of gas occurs on very long time scales (more than a hundred years), one needs to develop theoretical models to predict the material swelling. It has been shown previously that bitumen is a yield stress fluid and that, in the case of a motionless population (no migration due to buoyancy), the yield stress disturbs the classical scenario of nucleation, bubble growth and Ostwald ripening observed in a Newtonian fluid. In the present work, we consider bubbles nucleation and migration due to buoyancy and we show that the yield stress causes delays in the evolution of a bubble population and that it consequently modifies the macroscopic swelling of the material into the drums.