Europhys. Lett.
Volume 61, Number 6, March 2003
Page(s) 742 - 748
Section Electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics
Published online 01 March 2003
DOI: 10.1209/epl/i2003-00291-y
Europhys. Lett., 61 (6) , pp. 742-748 (2003)

Segregation by friction

L. Kondic1, R. R. Hartley2, S. G. K. Tennakoon2, B. Painter2 and R. P. Behringer2

1  Department of Mathematical Sciences & Center for Applied Mathematics & Statistics New Jersey Institute of Technology, Newark, NJ 07102, USA
2  Department of Physics and Center for Nonlinear and Complex Systems Duke University, Durham NC, 27708-0305, USA

(Received 7 August 2002; accepted in final form 21 December 2002)

Granular materials are known to separate by size under a variety of circumstances. Experiments presented here and elucidated by modeling and MD simulation document a new segregation mechanism, namely segregation by friction. The experiments are carried out by placing steel spheres on a horizontal plane enclosed by rectangular sidewalls, and subjecting them to horizontal shaking. Half the spheres are highly smooth; the remainder are identical to the first half, except that their surfaces have been roughened by chemical etching, giving them higher coefficients of friction. Segregation due to this difference in friction occurs, particularly when the grains have a relatively long mean free path. In the presence of an appropriately chosen small "hill" in the middle of the container, the grains can be made to completely segregate by friction type.

45.70.Mg - Granular flow: mixing, segregation and stratification.
46.55.+d - Tribology and mechanical contacts.
83.10.Rs - Computer simulation of molecular and particle dynamics.

© EDP Sciences 2003