Fluid Induced Particle Size Segregation in Sheared GranularAssembliesSitangshu

We perform a two-dimensional molecular-dynamics study of a model for sheared bidisperse granular systems under conditions of simple shear and Poiseuille ow. We propose a mechanism for particle-size segregation based on the observation that segregation occurs if the viscous length scale introduced by a liquid in the system is smaller than of the order of the particle size. We show that the ratio of shear rate to viscosity must be small if one wants to nd size segregation. In this case the particles in the system arrange themselves in bands of big and small particles oriented along the direction of the ow. Similarly, in Poiseuille ow we nd the formation of particle bands. Here, in addition, the variety of time scales in the ow leads to an aggregation of particles in the zones of low shear rate and can suppress size segregation in these regions. The results have been veriied against simulations using a full Navier-Stokes description for the liquid.