Papers »

Granular contacts in colloidal suspensions

The solid particles in a suspension need to reconfigure continuously during flow. The required stress for the flow increases with increasing volume fraction because motions of particles become to be more restricted by surrounding particles. The suspension will cease to flow if the volume fraction exceeds a certain value. This “jamming point” depends on several factors, including the nature of the interparticle force.

We have numerically reproduced discontinuous shear thickening of suspensions by introducing a granular-like contact model into Stokesian Dynamics simulations[1, 2]. Prior to shear thickening the particles interact hydrodynamically, with a stabilizing repulsive force; these interactions do not produce strong tangential forces. Above shear thickening, on the other hand, particles interact with frictional contact forces, hence tangential displacements of crowded particles are strongly hindered. We recently developed a stress-controlled simulation with periodic boundary conditions within an overdamped inertia-free (i.e., Stokesian Dynamicss) framework[3]. With stress control we obtain a complete set of non-monotonic flow curves for the steady-state shear rheology, which exhibits discontinuous shear thickening under rate control. We discuss whether the steady state flow is possible when the system is on the negative slope of an S-shaped flow curve.

[1] R. Seto, R. Mari, J. F. Morris, and M. M. Denn. Discontinuous shear thickening of frictional hard-sphere suspensions. Phys. Rev. Lett., 111:218301, 2013. doi: 10.1103/PhysRevLett.111. 218301.
[2] R. Mari, R. Seto, J. F. Morris, and M. M. Denn. Shear thickening, frictionless and frictional rheologies in non-brownian suspensions. J. Rheol., 58(6):1693–1724, 2014.
[3] R. Mari, R. Seto, J. F. Morris, and M. M. Denn. The non-monotonic flow curves of shear thickening suspensions. in preparation

Author(s):

Ryohei Seto    
Okinawa Institute of Science and Technology
Japan

Romain Mari    
Levich Institute, City College of New York
United States

Jeffrey Morris    
Levich Institute, City College of New York
United States

Morton Denn    
Levich Institute, City College of New York
United States