Micromechanical Modeling of Discontinuous Shear Thickening in Granular Media - Fluid 1 Suspension 2 3

15 Shear thickening in a fluid occurs when the viscosity of the fluid increases with 16 increasing applied strain rate. When the rise in viscosity occurs by orders of magnitude, the fluid 17 undergoes discontinuous shear thickening, which can be devastating in industrial applications. 18 We present a particle-scale numerical technique that can simulate these phenomena. By coupling 19 the discrete element method (DEM) and lattice Boltzmann method (LBM), we developed a 20 micromechanical model that can simulate the inter-particle stresses for particles that are 21 immersed in a fluid. A comparison of the simulation results against experimental results reported 22 in the literature demonstrates the potential of the method as a research tool. The comparison 23 included parametric studies to investigate the effects of solid fraction, particle-particle, and 24 particle-wall contact stiffness. With a systematic variation of the wall stiffness, the DEM-LBM 25 model demonstrates that increasing boundary stiffness directly increases the maximum shear 26 2 stress of the shear thickening regime. For the case of particles settling at low stresses, the DEM27 LBM model has the advantage of providing insight into particle-scale interactions in a detail not 28 possible using a continuum method based on phenomenological constitutive equations.We also 29 show that the central mechanism creating the shear thickening is the dilation of the particulate 30 media per traditional soil mechanics principles. 31 32