Flowing resistance and dilatancy of dense suspensions: lubrication and repulsion

8 pages - 5 figuresInternational audienceWe examine the flow properties of dense suspensions whose particles interact by viscous lubrication and surface repulsion. Using Soft Dynamics, we simulate its response to shear, prescribing the shear rate and the normal stress. We show that the behavior of steady flows can be described like that of dry grains, with a friction law and a dilatancy law. Their combination conveniently avoids the usual divergence of viscosity when approching the maximum packing fraction. However, the parameters of these laws depend in a non-trival way on the typical distance below which surfaces repel each other. The analysis of internal distribution of forces suggests a simple scenario underpining these complex dependencies. Pairs of particles appear to exchange a comparable lubrication force irrespective of their distance. This leads to a robust dynamic connected network controlling the collective resistance to flow