Hydrodynamic shear thickening of particulate suspension under confinement

We study the rheology of dense suspensions of non-Brownian repulsive particles. The suspensions consist of two-dimensional discoidal particles confined by walls orthogonal to the shear gradient direction and are simulated by the method of smoothed particle hydrodynamics. The strength of hydrodynamic shear thickening is primarily determined by the distribution of hydrodynamic clusters formed during shear flow while confinement plays a geometrical role and indirectly affects viscosity. Under strong confinement a percolating network of clusters develops into a jamming structure at high shear rate and as a result, the viscosity increases substantially. Extrapolating the viscosity to the limit of very weak confinement shows that confinement is essential to observe hydrodynamic shear thickening in these non-Brownian suspensions.