Liquid morphologies and capillary forces between three spherical beads

TL;DR

This study numerically investigates the equilibrium shapes and capillary forces of liquid bridges between three spherical beads, revealing bistability and force variations relevant to wet granular materials.

Contribution

It provides a detailed numerical analysis of liquid morphologies and capillary forces in a three-bead system, highlighting bistability and force differences between dimer and trimer configurations.

Findings

Identification of dimer and trimer morphologies in three-bead systems.

Observation of bistability between dimer and trimer during size variations.

Capillary forces depend on liquid volume and Laplace pressure, with trimers exerting slightly larger forces.

Abstract

Equilibrium shapes of coalesced pendular bridges in a static assembly of spherical beads are computed by numerical minimization of the interfacial energy. Our present study focuses on generic bead configurations involving three beads, one of which is in contact to the two others while there is a gap of variable size between the latter. In agreement with previous experimental studies, we find interfacial `trimer' morphologies consisting of three coalesced pendular bridges, and `dimers' of two coalesced bridges. In a certain range of the gap opening we observe a bistability between the dimer and trimer morphology during shrinking and growth. The magnitude of the corresponding capillary forces in presence of a trimer or dimer depends, besides the gap opening only on the volume or Laplace pressure of liquid. For a given Laplace pressure, the capillary forces in presence of a trimer are slightly larger than the force of a single bridges at the same gap opening, which could explain the shallow maximum and plateau of the capillary cohesion of a wetting liquid for saturations in the funicular regime.