Reversing the Brazil-Nut Effect : Competition between Percolation and Condensation

Titelangaben

Breu, Andreas P. J. ; Ensner, Hans-Martin ; Kruelle, Christof A. ; Rehberg, Ingo:
Reversing the Brazil-Nut Effect : Competition between Percolation and Condensation.
In: Physical Review Letters. Bd. 90 (2003) Heft 1 . - 014302.
ISSN 1079-7114
DOI: https://doi.org/10.1103/PhysRevLett.90.014302

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Abstract

We report on experiments on vertically shaken binary granular mixtures, which separate into their components due to the external excitation. This well-known phenomenon, where large particles rise to the top of the mixture, is called the Brazil-nut effect. Recent theoretical findings predict also a reverse Brazil-nut effect, where large particles sink to the bottom of the container. We choose spherical beads of various diameters and materials in order to observe the transition from Brazil-nut effect to its reverse form. The direction of demixing depends sensitively on the external excitation, so that it is possible to switch between both effects for a given mass density ratio.