Abstract
Studying the flow of granular materials is important for its impact on both industrial applications and natural phenomena. A fundamental understanding of the flow of granular materials is lacking, and this results in difficulties in modeling and predicting their flow behavior. The discrete element method (DEM) is often used as the “gold standard” both for predicting the results of experiments as well as for comparison to continuum-level theories of granular material flows due to its derivation from first-principal constructs, like contact mechanics. In this paper, we continue our work on quantitative validation of DEM simulations using detailed measurements of simple, well-characterized flows that allow us to examine the effect of rough surfaces and rotational rates on granular flow using an annular shear cell. Experimentally, we use digital particle tracking velocimetry (DPTV) to obtain velocity, solids fraction, and granular temperature profiles. Computationally, we compare the results obtained using different contact mechanics force laws to those from experimental measurements as well as perform a sensitivity analysis on device and particle geometry and different material properties employed. In previous work on stainless steel beads, we have found that an elasto-plastic normal force model is critical to obtaining accurate results as is detailed matching of both particle and system geometry, while the choice of friction model is found to be unimportant. Here, we examine the robustness of these observations to both particle materials properties as well as systemic variables (such as total system solids fraction). We find that the choice of frictional force model has little effect across all the profiles and all models, while the accuracy of the normal force model is material-dependent.
The discrete element method (DEM) is often used as the gold standard both for modeling and predicting the flow behavior of granular material flows, yet much of the validation of this technique has been largely indirect and qualitative. In this paper, we outline new work on quantitative validation of DEM simulations using detailed measurements of simple, well-characterized flows in an annular shear cell. Experimentally, we use digital particle tracking velocimetry (DPTV) to obtain velocity, solids fraction, and granular temperature profiles. Computationally, we compare the results obtained using different contact mechanics force laws. We find that the spring–dashpot model is the most accurate when polymeric beads are used in the experiments. [Display omitted]
•An annular shear cell is used to validate the discrete element method (DEM).•Careful matching of the system geometry is critical to accurate simulation.•Viscoelastic damping is more accurate for modeling polymer beads than other models.