**Flow regime transitions in dense non-Brownian suspensions: Rheology,
microstructural characterization, and constitutive modeling**

C Ness and J Sun, PHYSICAL REVIEW E, 91, 012201 (2015).

DOI: 10.1103/PhysRevE.91.012201

Shear flow of dense non-Brownian suspensions is simulated using the
discrete element method taking particle contact and hydrodynamic
lubrication into account. The resulting flow regimes are mapped in the
parametric space of the solid volume fraction, shear rate, fluid
viscosity, and particle stiffness. Below a critical volume fraction
phi(c), the rheology is governed by the Stokes number, which
distinguishes between viscous and inertial flow regimes. Above phi(c), a
quasistatic regime exists for low and moderate shear rates. At very high
shear rates, the phi dependence is lost, and soft-particle rheology is
explored. The transitions between rheological regimes are associated
with the evolving contribution of lubrication to the suspension stress.
Transitions in microscopic phenomena, such as interparticle force
distribution, fabric, and correlation length are found to correspond to
those in the macroscopic flow. Motivated by the bulk rheology, a
constitutive model is proposed combining a viscous pressure term with a
dry granular model presented by Chialvo et al. **Phys. Rev. E 85, 021305
(2012)**. The model is shown to successfully capture the flow regime
transitions.

Return to Publications page