Berlin 2012 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 32: Soft Matter II
DY 32.1: Vortrag
Freitag, 30. März 2012, 10:00–10:15, MA 144
Deformation of Platonic foam cells: Effect on growth rate — •Myfanwy Evans1, Johannes Zirkelbach1, Gerd Schröder-Turk1, Andrew Kraynik1,2, and Klaus Mecke1 — 1Theoretische Physik, Friedrich-Alexander Universität Erlangen-Nürnberg, Germany — 2Manchester, UK
Coarsening is the process by which gas diffuses through the films that separate foam cells, and causes them to grow or shrink over time. The growth rate for 2D foams is fully described by von Neumann's law, and relies solely on cell topology. The situation for 3D foams is poorly understood, despite claims to the contrary, where growth rate depends on that cell shape as well as topology. Isotropic Plateau polyhedra (IPP) are hypothetical 3D foam cells, composed of F regular spherical-capped faces, that fulfill Plateau's laws and enable an analytical solution for the growth rate in terms of F.
We use the Surface Evolver to model the deformation of Platonic foam cells that are suspended from wire frames. The deformed cells satisfy Plateau's laws when subjected to compression, extension, shear and torsion. For all three Platonic foams, which are the realisable IPP, we observe different responses in the growth rate to deformation, depending on cell type, deformation mode and frame size. The growth rate can increase or decrease with increasing cell distortions: in the case of pentagonal dodecahedron cells subjected to torsion, even the direction of diffusion can change. Our analysis of the relation between cell deformation and growth rate offers insight into the coarsening of real foams, where cells are not necessarily regular and isotropic.