Micromechanical modeling of discontinuous shear thickening in granular media-fluid suspension

Shear thickening in a fluid occurs when the viscosity of the fluid increases with the increasing applied strain rate. When the rise in viscosity occurs by orders of magnitude, the fluid undergoes discontinuous shear thickening, which can be devastating in industrial applications. We present a particle-scale numerical technique that can simulate these phenomena. By coupling the discrete element method (DEM) and lattice Boltzmann method (LBM), we developed a micromechanical model that can simulate the interparticle stresses for particles that are immersed in a fluid. A comparison of the simulation results against the experimental results reported in the literature demonstrates the potential of the method as a research tool. The comparison included parametric studies to investigate the effects of solid fraction, particle-particle, and particle-wall contact stiffness. With a systematic variation of the wall stiffness, the DEM-LBM model demonstrates that increasing boundary stiffness directly increases the maximum shear stress of the shear thickening regime. For the case of particles settling at low stresses, the DEM-LBM model has the advantage of providing insight into detailed particle-scale interactions, which is not possible using a continuum method based on phenomenological constitutive equations. We also show that the central mechanism creating the shear thickening is the dilation of the particulate media per traditional soil mechanics principles. (C) 2017 The Society of Rheology.