Rheology of dense particle suspensions in linear over-damped flow

Abstract: Suspensions are composed of mixtures of particles and fluid and are omnipresent in natural phenomena and in industrial processes. While hydrodynamic interactions or lubrication forces between the particles are important in the dilute regime, they become of lesser significance when the concentration is increased, and direct particle contacts become dominant in the rheological response of concentrated suspensions, particularly those close to the maximum volume fraction where the suspension ceases to flow. The mixture of particles and fluid can be seen as a fluid with effective rheological properties but also as a two-phase system wherein the fluid and particles can experience relative motion. By introducing a numerical scheme including both hydrodynamic interactions and grnularlike contacts for dense particle suspensions in overdamped linear flows, we show that contact friction is essential for having DST. Above a critical volume fraction, we observe the existence of two states: a low viscosity, contactless (hence, frictionless) state, and a high viscosity frictional shear jammed state. These two states are separated by a critical shear stress, associated with a critical shear rate where DST occurs. Potential strategies to extend the present methodology to non-spherical particles are also demonstrated and explained for very concentrated suspensions but due to the cumbersome numerical model we will present the results in the future works.