Slow viscoelastic relaxation and aging in aqueous foam

TL;DR

This paper investigates the slow viscoelastic relaxation and aging in aqueous foams, revealing that coarsening-induced bubble rearrangements drive long-term relaxation and follow a Poisson process, aligning with experimental data.

Contribution

It demonstrates that coarsening-induced bubble rearrangements are the physical origin of slow relaxation in foams, supported by simulations and scaling laws.

Findings

Long-time relaxation driven by coarsening-induced rearrangements

Rearrangements follow a Poisson process

Simulation results agree with experimental scaling laws

Abstract

Like emulsions, pastes and many other forms of soft condensed matter, aqueous foams present slow mechanical relaxations when subjected to a stress too small to induce any plastic flow. To identify the physical origin of this viscoelastic behaviour, we have simulated how dry disordered coarsening 2D foams respond to a small applied stress. We show that the mechanism of long time relaxation is driven by coarsening induced rearrangements of small bubble clusters. These findings are in full agreement with a scaling law previously derived from experimental creep data for 3D foams. Moreover, we find that the temporal statistics of coarsening induced bubble rearrangements are described by a Poisson process.