Abstract
Dynamic particle-scale numerical simulations are used to study the variation of microstructure with shear stress during shear thickening in dense non-Brownian suspensions. The microscale information is used to characterize the differences between the shear thickened (frictional) and non-thickened (lubricated, frictionless) states. Here, we focus on the force and contact networks and study the evolution of associated anisotropies with increase in shear stress. The force and contact networks are both more isotropic in the shear-thickened state than in non-thickened state. We also find that both force and structural anisotropies are rate independent for both low and high stress, while they are rate (or stress) dependent for the intermediate stress range where the shear thickening occurs. This behavior is similar to the evolution of viscosity with increasing stress, showing a clear correlation between the microstructure and the macroscopic rheology.
Highlights
Suspensions are dispersions of rigid particles in fluids
The viscosity increases with increase in shear rate and is termed continuous shear thickening (CST)
At high volume fraction the viscosity can increase by orders of magnitude at a critical shear rate in what is known as discontinuous shear thickening (DST) [1, 3]
Summary
The fluid allows numerous possible interactions between the particles, but here we consider only hydrodynamic interactions and short-range or contact forces. Even with this simple system, a rich rheology is found, including shear thinning or shear thickening, normal stress differences, particle migration, shear jamming and yield stress behavior [1,2,3]. The viscosity increases with increase in shear rate (or shear stress) and is termed continuous shear thickening (CST). At high volume fraction the viscosity can increase by orders of magnitude at a critical shear rate in what is known as discontinuous shear thickening (DST) [1, 3]. We explore features of this lubricatedfrictional transition through numerical simulations
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