Balancing size and density segregation in bidisperse dense granular flows

Multi-Scale Mechanics Group, Dept. of Thermal and Fluid Engineering, University of Twente, Enschede, The Netherlands.

^* e-mail: d.r.tunuguntla@utwente.nl
^** e-mail: a.r.thornton@utwente.nl

Published online: 30 June 2017

Abstract

Several experimental studies have illustrated a balance between the segregation forces arising due to size- and density-differences. However, no detailed studies have been carried out to quantify this balance. In 2014, by utilising discrete particle simulations, we presented a simple relationship between the particle size-and density-ratio, $${\widehat{s}}^a=\widehat{\rho }$$, where ‘a’ determines whether the partial pressure scales with the diameter, surface area or volume of the particle. For a 50:50 mix (in volume) of bidisperse granular mixtures, we found the partial pressure to scale with the volume of the particle, i.e. a = 3. Moreover, there also exists a range of size- and density-ratios that satisfy the relation $${\widehat{s}}^3=\widehat{\rho }$$, where the bidisperse mixture remains homogeneously mixed. However, in this proceeding, we deviate from the conventional 50:50 mixes and consider a slightly extreme case of mixes, such as the 10:90 (in volume) mixes, which are often found in nature and industries. By doing so we observe that the partial pressure does not scale with the particle volume and, more importantly, the zero-segregation relation is not as simple as $${\widehat{s}}^a=\widehat{\rho }$$. However, there does exist a range of size- and density-ratios for which the mixture weakly segregates.