Daisy-shaped liquid bridges in foam-filled granular packings

Hypothesis: Many applications of liquid foams use them to fill the porosity of various granular media. How is the liquid distributed in such foam-filled systems, in which the geometry of the bubble assembly can be strongly constrained by pore confinement? Experiments: We study how the liquid is distributed in a grain packing filled with liquid foam, as a function of both liquid content and bubble-to-grain size ratio. Moreover, Surface Evolver simulations are carried out at the scale of a single bubble confined into a tetrahedral pore. Findings: We reveal that foam-filled granular assemblies exhibit a robust pendular-like regime, which is reminiscent of the pendular regime in unsaturated media. The main difference is that here the liquid bridges are daisy-shaped, i.e. with a liquid core bounded by bubbly petals. A simple theoretical model is proposed to describe the foam liquid bridges between contacting grains. In the case of large bubbles, the model is compared with the Surface Evolver simulation. The model is also applied to the case of wall liquid bridge, which is compared with the experimental observation. Beyond their geometrical characteristics, the presence of these liquid bridges, which can represent almost 25% of the liquid contained in the porosity, makes it possible to imagine a new approach (binder foam-based) to bind granular assemblies and turn them to solid materials. (c) 2023 Elsevier Inc. All rights reserved.

Automated summary

This study investigates the distribution of liquid in foam-filled granular media under pore confinement. The findings reveal a pendular-like regime in the foam-filled granular assemblies, with daisy-shaped liquid bridges between the grains. A theoretical model is proposed to describe the foam liquid bridges, which can potentially be used to bind granular assemblies and transform them into solid materials.