Energy characteristics of simple shear granular flows

This work uses a 3-D discrete element simulation to calculate the elastic and kinetic energy for a nonuniform granular shear flow to determine whether the ratio of these energies is sufficient to identify specific flow regimes of granular materials in a fashion to other dimensionless parameters such as inertial number and dimensionless stiffness. We first obtain the critical packing fraction under isostatic compression, then analyze the mean and fluctuating parts of the elastic and kinetic energy as the granular flow reaches a steady state. External work performed on a system during granular flow partially dissipates into heat, while the remaining work is stored in particles as elastic and kinetic energy; thus processes occurring at a particle level not only control the energy transformation, but also affect the bulk behavior of a granular flow. The effective frictions are correlated with the mean elastic energy to mean kinetic energy ratio and it is interesting to find a power law function with an index of $-0.16$ for the systems used in this work. Analysis of this ratio’s ability to classify flow shows that its determination is quite sufficient to identify specific flow regimes of granular materials, even though energy has a scalar expression. Therefore, these energetics studies can provide a theoretical basis for unifying the mechanics of granular flows over the entire range of regimes.