Particle-induced transition in foams

TL;DR

This study investigates how particle size, bubble size, and gas volume fraction influence the mobility of the interstitial phase in particulate foams, revealing a sharp transition controlled by a parameter bbb, which determines whether particles drain freely or become trapped.

Contribution

It introduces a control parameter bbb that predicts the transition between free drainage and particle trapping in particulate foams based on geometric ratios.

Findings

Particles drain freely when bbb < 1.

Particles become trapped and reduce mobility when bbb > 1.

Mobility depends strongly on bubble size, particle size, and gas volume fraction.

Abstract

The macroscopic behaviour of foams is deeply related to rearrangements occurring at the bubble scale, which dynamics depends on the mobility of the interstitial phase. In this paper, we resort to drainage experiments to quantify this mobility in particulate foams, where a particle suspension is confined between foam bubbles. Results show a strong dependence on each investigated parameter, i.e. bubble size, particle size and gas volume fraction for a given particle volume fraction. A combination of these parameters has been identified as the control parameter \lambda, which compares the particle size to the size of passage through constrictions within the foam pore space. \lambda\ highlights a sharp transition: for \lambda\ < 1 particles are free to drain with the liquid, which involves the shear of the suspension in foam interstices, for \lambda\ > 1 particles are trapped and the mobility of the interstitial phase is strongly reduced.