Dense suspensions of particles in viscous liquid often demonstrate the striking phenomenon of abrupt shear thickening, where their viscosity increases strongly with increase of the imposed stress or shear rate. In this work, discrete-particle simulations accounting for short-range hydrodynamic, repulsive, and contact forces are performed to simulate flow of shear thickening bidisperse suspensions, with the packing parameters of large-to-small particle radius ratio δ = 3 and large particle fraction ζ = 0.15, 0.50, and 0.85. The simulations are carried out for volume fractions 0.54 ≤ ϕ ≤ 0.60 and a wide range of shear stresses. The repulsive forces, of magnitude F R , model the effects of surface charge and electric double-layer overlap, and result in shear thinning at small stress, with shear thickening beginning at stresses σ ∼ F R a −2 . A crossover scaling analysis used to describe systems with more than one thermodynamic critical point has recently been shown to successfully describe the experimentally-observed shear thickening behavior in suspensions. The scaling theory is tested here on simulated shear thickening data of the bidisperse mixtures, and also on nearly monodisperse suspensions with δ = 1.4 and ζ = 0.50. Presenting the viscosity in terms of a universalmore »
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Shear thickening in dense bidisperse suspensions
Discrete-particle simulations of bidisperse shear thickening suspensions are reported. The work considers two packing parameters, the large-to-small particle radius ratio ranging from [Formula: see text] (nearly monodisperse) to [Formula: see text], and the large particle fraction of the total solid loading with values [Formula: see text], 0.5, and 0.85. Particle-scale simulations are performed over a broad range of shear stresses using a simulation model for spherical particles accounting for short-range lubrication forces, frictional interaction, and repulsion between particles. The variation of rheological properties and the maximum packing fraction [Formula: see text] with shear stress [Formula: see text] are reported. At a fixed volume fraction [Formula: see text], bidispersity decreases the suspension relative viscosity [Formula: see text], where [Formula: see text] is the suspension viscosity and [Formula: see text] is the suspending fluid viscosity, over the entire range of shear stresses studied. However, under low shear stress conditions, the suspension exhibits an unusual rheological behavior: the minimum viscosity does not occur as expected at [Formula: see text], but instead decreases with further increase of [Formula: see text] to [Formula: see text]. The second normal stress difference [Formula: see text] acts similarly. This behavior is caused by particles ordering into a layered more »
- Publication Date:
- NSF-PAR ID:
- 10380967
- Journal Name:
- Journal of Rheology
- Volume:
- 67
- Issue:
- 1
- Page Range or eLocation-ID:
- 91 to 104
- ISSN:
- 0148-6055
- Sponsoring Org:
- National Science Foundation
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