(388d) Rigid Structures in Frictional Dense Suspensions

In concentrated suspensions of neutrally buoyant particles, the apparent viscosity is often found to undergo an abrupt increase making a transition from a low-viscosity to a high-viscosity state, termed discontinuous shear thickening (DST)¹. The observed behavior has recently been linked to a transition from an unconstrained "lubricated" rheology, where close interactions between suspended particles take place through a thin liquid film, to a constrained "frictional" rheology, where particles make unlubricated frictional contacts^2,3. Particle simulations that led to this concept have been successful in quantitatively reproducing the non-Newtonian behavior of thickening suspensions^3–5. However, none of these studies have moved beyond the mean-field description and analyzed the rigidity of the underlying evolving frictional force network. Here, we use the pebble-game algorithm to decompose the simulated frictional contact networks into so-called “rigid clusters” which are the minimally rigid portions of the contact network. In dry granular literature, the emergence of rigidity is often associated with the onset of jamming⁶. However, we find the emergence of system-spanning rigid clusters at volume fractions below the frictional jamming point. These results move beyond the current mean-field description and provide a new way to understand the onset of rigidity in shear thickening suspensions.

References:

1. Morris, J. F. Shear Thickening of Concentrated Suspensions: Recent Developments and Relation to Other Phenomena. Annu. Rev. Fluid Mech. 52, 121–144 (2020).
2. Seto, R., Mari, R., Morris, J. F. & Denn, M. M. Discontinuous Shear Thickening of Frictional Hard-Sphere Suspensions. Phys. Rev. Lett. 111, 218301 (2013).
3. Singh A., Mari R., Denn M.M., Morris J.F. A constitutive model for simple shear of dense frictional suspensions. J. Rheol. 62, 457–468 (2018).
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5. Singh, A., Ness, C., Seto, R., de Pablo, J. J. & Jaeger, H. M. Shear Thickening and Jamming of Dense Suspensions: The “Roll” of Friction. Phys. Rev. Lett. 124, 248005 (2020).
6. Henkes, S., Quint, D. A., Fily, Y. & Schwarz, J. M. Rigid Cluster Decomposition Reveals Criticality in Frictional Jamming. Phys. Rev. Lett. 116, 028301 (2016).