Simulation of dense non-Brownian suspensions with the lattice Boltzmann method: shear jammed and fragile states

Abstract

Dense non-Brownian suspensions including both the hydrodynamic interactions and the frictional contacts between particles are numerically studied under simple and oscillatory shears in terms of the lattice Boltzmann method. We successfully reproduce the discontinuous shear thickening (DST) under a simple shear for bulk three-dimensional systems. For our simulation of an oscillatory shear in a quasi-two-dimensional system, we measure the mechanical response when we reduce the strain amplitude after the initial oscillations with a larger strain amplitude. Here, we find the existence of the shear-jammed state under this protocol in which the storage modulus G is only finite for high initial strain amplitude γ I 0 . We also find the existence of the fragile state in which both fluid-like and solid-like responses can be detected for an identical area fraction and an initial strain amplitude γ I 0 depending on the initial phase Θ (or the asymmetricity of the applied strain) of the oscillatory shear. We also observe the DST-like behavior under the oscillatory shear in the fragile state. Moreover, we find that the stress anisotropy becomes large in the fragile state. Finally, we confirm that the stress formula based on the angular distribution of the contact force recovers the contact contributions to the stress tensors for both simple and oscillatory shears with large strains. arXiv:1904.02929v3 [cond-mat.soft]

Shear modulus and reversible particle trajectories of frictional granular materials under oscillatory shear

“…The friction causes drastic changes in rheology. For example, frictional particles exhibit discontinuous shear thickening [29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47] and shear jamming [48,49,50,51,52,53,54,55,56,57], which hardly occurs in frictionless particles. Thus, it is natural to expect that the friction between the grains affects the mechanical responses and particle trajectories.…”

Preparation and characterization of imidazolyl ionic liquid‐based shear thickening dispersion system

“…The purpose of additives is to improve the interaction between particles and solvents, or to improve the force between particles by modifying the particle surface. 29 Jianhao Ge et al used SiO 2 nanoparticles with 56% volume fraction and PEG 400 solvent to prepare STF. As a result, the solid phase volume fraction in STF was kept constant at 56%.…”

“…From the perspective of composition, in addition to the dispersed phase particles and the dispersion medium, an appropriate amount of additives can be added to the STF. The purpose of additives is to improve the interaction between particles and solvents, or to improve the force between particles by modifying the particle surface 29 . Jianhao Ge et al used SiO 2 nanoparticles with 56% volume fraction and PEG 400 solvent to prepare STF.…”

Impact-induced hardening in dense frictional suspensions

“…Similarly, numerical simulation is an important tool to understand the microscopic mechanism behind exotic phenomena in suspensions since the motion of the suspended particles is not visible in three-dimensional experiments. One of the remarkable insights from simulations is that the frictional contacts between particles are important for ob-serving DST under simple shear [8][9][10][11][12]. Nevertheless, a particle-based simulation of a free-falling projectile hitting a suspension has not been reported so far because of the difficulty of simulating suspension with free surface.…”

“…F g i = −m i g ẑ is the gravitational force acting on the suspended particles, where g is the gravitational acceleration and ẑ is the unit vector in the vertical direction. Note that our LBM accounts for both the short and the long-range parts for the hydrodynamic force F h i and torque T h i [12,20,21], though some previous simulations contains only the short-range force [9,10]. The contact forces F c ij and torques T c ij are computed using the linear-dashpot model with Coulomb friction rules and friction coefficient µ [22].…”