Coalescence and fracture of gas-liquid foams

Dr. Peter Stewart (University of Glasgow)

Thursday 14th November, 2013 14:00-15:00 Maths 326

Abstract

We construct a large-scale network model for the dynamics and stability of gas-liquid foams which explicitly incorporates hydrodynamic effects in the liquid films between adjacent gas bubbles. We use two example problems to demonstrate how these microscale flows can play a significant role in determining the macroscale behaviour of the foam. Firstly, we consider batch processing of high-porosity metallic solids from molten metal foams (produced without surfactant) where the liquid bridges separating adjacent bubbles drain rapidly and break due to inter-molecular attractions, leading to bubble coalescence. We characterise this coalescence process over both short and long timescales, and demonstrate that the evolution of the foam is remarkably self-similar over a wide range of parameter space. Secondly, we consider the fracture of (aqueous) gas-liquid foams under an applied driving pressure, elucidating the two distinct fracture modes observed in experiment which are analogous to the brittle and ductile failure mechanisms of crystalline solids.

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