On the particle pressure and normal stress differences of dense non-Brownian suspensions of frictionless particles in viscous and inertial regimes

In this work we explore the non-Newtonian rheology of dense non-Brownian frictionless suspensions close to jamming using a Discrete Element Method. With increasing shear rate the rheology of the suspension displays a transition from a viscous scaling of constant viscosity to a Bagnoldian scaling wherein the viscosity scales linearly with the shear-rate. We report on the scalings for the particle pressure, first and second normal stress differences within the suspension in both the viscous and inertial regimes. The results indicate that the macroscopic friction coefficient for the suspension vanishes as we approach jamming. We argue that this phenomenon is linked to the orientation of microstructural elements within the suspension.