On Improving the Calibration and Validation of Computer Simulations for Bulk Materials Handling Systems

Discrete or Distinct Element Method (DEM) is proving to be a reliable and effective tool to model the behaviour of granular bulk materials. Numerous particle-scale (microscopic) mechanisms influence the bulk (macroscopic) behaviour of granular flow. Hence, it is important that the relevant input parameters for DEM be determined by actual physical “calibration” experiments, and not be assumed based on other information or experience. It is equally important that each calibration test be checked and validated in terms of the relevant physics involved. This paper describes some of the bench-scale experiments that have been developed to calibrate the DEM simulations to reflect actual dynamic behaviour. Relevant parameters such as static friction coefficient, rolling friction coefficient, shear modulus, coefficient of restitution, particle geometry (e.g. particle size and shape) and inter-particle forces (e.g. cohesion due to liquid bridges) have been investigated and employed to model and estimate bulk characteristics and behaviour, such as the poured and drained angles of repose and solids mass flow rate. It has been found that traditional “slump” tests are operator and “system” dependent and can produce misleading and inaccurate results. These bench-scale tests have been modified to eliminate such dependencies. The resulting DEM simulations have been validated using a high-speed camera to capture and quantify actual static and dynamic characteristics.