Rheology near jamming: The influence of lubrication forces

Abstract

We study, by computer simulations, the role of different dissipation forces on the rheological properties of highly-dense particle-laden flows. In particular, we are interested in the close-packing limit (jamming) and the question if "universal" observables can be identified that do not depend on the details of the dissipation model. To this end, we define a simplified lubrication force and systematically vary the range hc of this interaction. For fixed hc a cross-over is seen from a Newtonian flow regime at small strain rates to inertia-dominated flow at larger strain rates. The same cross-over is observed as a function of the lubrication range hc. At the same time, but only at high densities close to jamming, single-particle velocities as well as local density distributions are unaffected by changes in the lubrication range -they are candidates for "universal" behavior. At densities away from jamming, this invariance is lost: short-range lubrication forces lead to pronounced particle clustering, while longer-ranged lubrication does not. These findings highlight the importance of "geometric" packing constraints for particle motion -independent of the specific dissipation model. With the free volume vanishing at random-close packing, particle motion is more and more constrained by the ever smaller amount of free space. On the other side, macroscopic rheological observables, as well as higher-order correlation functions retain the variability of the underlying dissipation model.

Unified theory of inertial granular flows and non-Brownian suspensions

“…To be in the overdamped universality class, motion along floppy modes must be damped. When the drag is purely associated to longitudinal motion between particles in contact, or nearly in contact, the flow curves depend on the gap cutoff below which this drag is applied: inertial when only touching particles dissipate energy [11], and viscous otherwise [37]. This observation, which has been interpreted as a failure of universality, is natural from the present approach, since motion transverse to contacts dominates near jamming.…”

“…Experiments [9] and simulations [10,11,37,38] report a transition from viscous to inertial flows as the strain ratė is increased at fixed packing fraction. For hard frictionless particles, the location of this transition can be computed precisely in our framework.…”

Effects of crystal shape‐ and size‐modality on magma rheology

“…A number of studies of concentrated liquidparticle suspensions have been motivated by an interest in unifying suspension and granular rheology [e.g., Jop et al, 2006;Boyer et al, 2011;Lerner et al, 2012;Maiti and Heussinger, 2014]. By combining the effect of both frictional and hydrodynamic forces, Boyer et al a.…”

Stress fluctuations and shear thickening in dense granular suspensions

“…As a critical volume fraction is approached, a steep jump in flow resistance with shear rate can be observed, a phenonmenon called discontinuous shear thickening (DST) 4,7,[9][10][11] . However, viscous interactions can also be significant in suspensions as grains are close to each other at high volume fractions 12,13 . For instance, the contribution of lubrication forces to shear thickening has been discussed extensively.…”