Segregation transitions in wet granular matter

A. Samadani and A. Kudrolli

Nonlinear Physics Laboratory, Clark University

 


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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.
 

Figure shows the effect of adding a small volume fraction of fluid to bidisperse glass beads. (a) corresponds to the dry case and (d) where 1% by volume of water has been mixed into the granular mixture before pouring.


Preprints:

  1. ``Segregation transitions in wet granular matter," A. Samadani and A. Kudrolli, Phys. Rev. Lett. 85, 5102 (2000)
  2. ``Segregation and layering in the flow of wet granular matter," A. Samadani and A. Kudrolli, Proceedings of Powders and Grains 2001 (in press)
  3. ``Size Segregation of Granular Matter in Silo Discharges," A. Samadani, A. Pradhan, and A. Kudrolli Phys. Rev E 60, 7203 (1999).

 

Arshad Kudrolli

Department of Physics  

Clark University

Worcester, MA 01610


Last modified: April 13, 2000

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