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Stability of freely falling granular streams.

Authors
  • Ulrich, Stephan
  • Zippelius, Annette
Type
Published Article
Journal
Physical Review Letters
Publisher
American Physical Society
Publication Date
Oct 19, 2012
Volume
109
Issue
16
Pages
166001–166001
Identifiers
PMID: 23215093
Source
Medline
License
Unknown

Abstract

A freely falling stream of weakly cohesive granular particles is modeled and analyzed with the help of event driven simulations and continuum hydrodynamics. The former show a breakup of the stream into droplets, whose size is measured as a function of cohesive energy. Extensional flow is an exact solution of the one-dimensional Navier-Stokes equation, corresponding to a strain rate, decaying like t(-1) from its initial value, γ[over ˙](0). Expanding around this basic state, we show that the flow is stable for short times, γ[over ˙](0)t<<1, whereas for long times, γ[over ˙](0)t>>1, perturbations of all wavelengths grow. The growth rate of a given wavelength depends on the instant of time when the fluctuation occurs, so that the observable patterns can vary considerably.

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