Rheology near jamming: The influence of lubrication forces

Moumita Maiti, Claus Heussinger
2014 Physical Review E  
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 h_c of this interaction. For fixed h_c a cross-over is seen from a
more » ... 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 h_c. At the same time, but only at high densities close to jamming, particle velocity 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 universality 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.
doi:10.1103/physreve.89.052308 pmid:25353801 fatcat:tbprkl6ymrarpbnqywszilv2ju