Calibration of the DEM sliding friction and rolling friction parameters of a cohesionless bulk material

The discrete element method (DEM) has become a valuable tool for understanding the mechanical behaviour of granular assemblies, however, the accuracy of the DEM simulations depends on several interaction parameters such as the sliding friction and rolling friction coefficients. Generally, these parameters are estimated using bulk calibration approach (BCA) where the draw down test has been suggested as an effective way to approach these coefficients. This test provides up to four bulk criteria, the angle of repose, shear angle, mass flow rate and the mass loss which are used to narrow down the possible coefficients. However, there is still more research needed around it to fully understand how this methodology works. An experimental and numerical study was carried out using the draw down test to assess the influence of different mass flow rates and particle shapes on DEM parameters for a cohesionless bulk material. It is concluded that use of multi-sphere particles and three aperture sizes in the draw down test to calibrate the sliding and rolling friction parameters of a cohesionless bulk material can converge to a small feasible region in which a single combination of the friction coefficients can be selected. The calibrated sliding and rolling friction coefficients were validated using multi-sphere particles, where the maximum deviation was 5.9% from the experimental values.