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Soft Matter and Biological Physics

Eur. Phys. J. E 5, 441-444 (2001)

Time of avalanche mixing of granular materials in a half filled drum

S.N. Dorogovtsev1, 2 and J.F.F. Mendes1

1  Departamento de Física and Centro de Física do Porto, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal
2  A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia


(Received 27 October 2000 and Received in final form 13 March 2001)

The avalanche mixing of granular solids in a slowly rotated 2D upright drum is studied. We demonstrate that the account of the difference $\delta$ between the angle of marginal stability and the angle of repose of the granular material leads to a restricted value of the mixing time $\tau$ for a half filled drum. The process of mixing is described by a linear discrete difference equation. We show that the mixing looks like linear diffusion of fractions with the diffusion coefficient vanishing when $\delta$ is an integer part of $\pi$. Introduction of fluctuations of $\delta$ suppresses the singularities of $\tau(\delta)$ and smoothes the dependence $\tau(\delta)$.

64.75.+g - Solubility, segregation, and mixing; phase separation.
45.70.Mg - Granular flow: mixing, segregation and stratification.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001