(317e) Shear Reversal in Cohesive Frictional Dense Suspensions: A Numerical Study

Dense suspensions are dispersions of small particles in a Newtonian solvent that are ubiquitous in nature and industry. The presence of various surface interactions and particle properties such as size, roughness, interfacial chemistry, and shape manifests itself as various non-Newtonian rheological features such as yielding, shear thinning, shear thickening, and jamming. In this work, we use a simulation tool LF-DEM that combines lubrication flow (LF) with discrete element method (DEM) to simulate inertialess buoyant particles dispersed in a Newtonian solvent. We include DLVO potential, including attractive and repulsive forces with hydrodynamic and contact friction. The yield stress is observed at low-stress states for strong enough attraction, which increases with particle loading and strength of attraction. To elucidate the role of different types of attraction, we employ shear reversal under constant shear stress. In the absence of attractive forces, frictional contacts break down under shear reversal. At a high enough strength of attraction, attractive forces help stabilize the frictional forces under shear reversal. We also find distinct network features at yielding compared to the shear-thickened or jammed states.