(464j) Influence of Attractive Forces and Particle Size Distribution on Shear Thickening of Suspensions

Authors: 
Pednekar, S., Levich Institute and Department of Chemical Engineering, City College of New York
Morris, J. F., City College of New York
Chun, J., Pacific Northwest National Laboratory
The shear thickening of suspensions includes a remarkable phenomenon termed â??discontinuous shear thickeningâ? in which the viscosity of a suspension can increase several orders of magnitude as the shear rate is increased over a small range. This increase may have dramatic impact on applications. The transition from a lubricated to a â??frictionalâ? rheology due to the contribution of contact forces has been identified as one mechanism for shear thickening in suspensions. Recent simulations have been successful in quantitatively reproducing experimentally-observed, continuous and discontinuous shear thickening for both Brownian and non-Brownian suspensions [1-2]. A related experimental observation [3] is that attractive forces can lead to large low-shear viscosity and potentially yield stress, with the result that shear-thinning occurs and shear thickening is obscured. Here, we will show that this behavior is captured by our simulation tool including hydrodynamic effects, contact and friction, as well as attractive colloidal forces. We study the impact of various cohesion strengths on shear thickening curves at various suspension concentrations. We also investigate the non-trivial effect of particle size distribution, which may manifest itself through differences in inter-particle interactions (repulsive or attractive) and effective maximum packing increase.

[1] Seto, Ryohei, et al. "Discontinuous shear thickening of frictional hard-sphere suspensions." Physical Review Letters 111.21 (2013): 218301.

[2] Mari, Romain, et al. "Discontinuous shear thickening in Brownian suspensions by dynamic simulation." Proceedings of the National Academy of Sciences 112.50 (2015): 15326-15330.

[3] Gopalakrishnan, V., and C. F. Zukoski. "Effect of attractions on shear thickening in dense suspensions." Journal of Rheology (1978-present) 48.6 (2004): 1321-1344.