Dresden 2014 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 41: Poster - Pattern/ Nonlinear Dyn./ Fluids/ Granular/ Critical Phen.
DY 41.23: Poster
Donnerstag, 3. April 2014, 17:00–19:00, P3
Packing of hard spheres in cylinders and applications — •Adil Mughal1, Denis Weaire2, Ho Kei Chan2, and Stefan Hutzler2 — 1Institut fur Theoretische Physik, Friedrich-Alexander Universitat Erlangen-Nurnberg, Staudtstr. 7, D-91058 Erlangen, Germany — 2School of Physics, Trinity College, Dublin 2, Republic of Ireland
We study the optimal packing of hard spheres in an infinitely long cylinder. Our simulations have yielded dozens of periodic, mechanically stable, structures as the ratio of the cylinder (D) to sphere (d) diameter is varied. Up to D/d=2.715 the densest structures are composed entirely of spheres which are in contact with the cylinder. The density reaches a maximum at discrete values of D/d when a maximum number of contacts are established. These maximal contact packings are of the classic "phyllotactic" type, familiar in biology. However, between these points we observe another type of packing, termed line-slip.
An analytic understanding of these rigid structures follows by recourse to a yet simpler problem: the packing of disks on a cylinder. We show that maximal contact packings correspond to the perfect wrapping of a honeycomb arrangement of disks around a cylindrical tube. While line-slip packings are inhomogeneous deformations of the honeycomb lattice modified to wrap around the cylinder.
Beyond D/d=2.715 the structures are more complex, since they incorporate internal spheres. We review some relevant experiments with hard spheres, small bubbles and discuss similar structures found in nature. We discuss the chirality of these packings and potential applications in photonics.