Discrete element investigation of stress fluctuation in granular flow at high strain rates

The high rate shear of a granular material is investigated by the use of a discrete mesodynamic method. The simulation describes a Couette flow geometry without gravity. A collection of frictional and perfectly smooth particles are subjected to strain rates ranging from $\frac{2}{3}\times {10}^1$ to $\frac{2}{3}\times {10}^{4}1/\mathrm{s}$ at solids concentrations ranging from 75% to 87% in a two-dimensional geometry. Normal stresses at the base of the granular sample are recorded. Large fluctuations in individual transmitted stresses are observed. The behavior of this stress profile compares well with previous experimental results. A near linear relation between normal stress and the strain rate is observed. The mechanism of stress transfer, stress chain formation, and random particle collision, through the depth of the sample, is seen to depend on solids concentration. Friction affects both the magnitudes of normal stresses and the characteristics of the granular flow.