On the Validation of a Differential Variational Inequality Approach for the Dynamics of Granular Material

The validation of a DVI approach for the dynamics of granular material project focuses on comparing the experimental and simulation results of granular flow for two tests in the Chrono::Engine simulation environment. An aluminum rig was designed and fabricated to measure the mass flow rate of a given amount of granular material flowing due to gravity through a slit. The mass flow rate was initiated by using a Newport UMR8.25 translational stage and Newport LTA-HL precision linear actuator to open and close the slit steadily. Once the slit was open, the weight of the granular material was transmitted to the processor via a router connected to a Cooper LFS242 Tension/Compression Cell (Serial No. 286284) and graphed over time. A model of the flow meter was created in Chrono::Engine and the results were matched to experimental runs by changing the friction coefficient between particles. After the friction coefficient of the particles was determined to be 0.15, several experimental runs with differing slit sizes were run. These flow rates were compared to the mass versus time data that Chrono::Engine output for the corresponding slit size. Runs for gap sizes of 1.5 mm, 2 mm, 2.5 mm, and 3 mm were performed with 0.0624 N of granular material, which amounted to approximately 40,000 bodies. These gap sizes corresponded to an experimental flow rate of 1. Chrono::Engine had less than a 2% error in calculating the flow rate of the granular material through a slit. In addition to comparing mass flow rates, the pile repose angle from the experimental runs was compared to the simulation results.