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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 changes of the liquid volume. 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 the liquid. For a given Laplace pressure, and for the same
gap opening, the capillary forces induced by a trimer are only slightly larger than the corresponding forces in the
presence of three pendular bridges. This observation is consistent with a plateau of capillary cohesion in terms
of the saturation of a wetting liquid in the funicular regime, as reported in the experimental work [Scheel et al.,
Nat. Mater. 7, 189 (2008)].
