Segregation transitions in wet granular matter
A. Samadani and A. Kudrolli
Nonlinear Physics Laboratory, Clark University
Segregation in granular matter can be benefit or a nuisance. Remarkable sensitivity to small differences in the size, shape and density of the constituent grains has been observed. However, most of this work relates to noncohesive granular matter. We investigate the progress of segregation in the presence of interstitial fluid by imaging the pile that results after bidisperse color-coded particles are poured into a silo. A sharp reduction of segregation is observed when a small volume fraction of fluid V_f is added which introduces capillary bridges between particles. Preferential clumping of small particles is observed to cause layering at small V_f. We obtain the segregation phase diagram as a function of size ratio r of the bidisperse particles and V_f. We show the importance of the viscous force in addition to the capillary force on both the progress of segregation and the angle of repose theta by changing the viscosity of the fluid. We find that the sharp change in the extent of segregation and theta occurs over similar V_f. A second transition to segregation depending on viscosity is observed when the particles are completely immersed in the fluid.
Preprints:
Clark University
Worcester, MA 01610
Last modified: April 13, 2000
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