Nor-Edine Abriak

A study of shape non-uniformity and poly-dispersity in hopper discharge of spherical and polyhedral particle systems using the Blaze-DEM GPU code

The importance of shape non-uniformity and the polydispersed nature of granular media in industrial hopper discharge applications has been well established experimentally. Although numerous hopper discharge simulations have been conducted over the last thirty years, the investigations into the non-uniformity of particle shape and the polydisperse nature of particle systems remains limited. These studies are usually limited to a single hopper configuration, while the number of polyhedral particles considered are usually limited to a maximum of 5000 particles. In this study we consider the polydispersed particle systems for hoppers at various angles, particle systems with non-uniform shape for hoppers at various angles and polyhedral particle systems up to 1 million particles. This is made possible by extensively utilizing the graphical processing unit (GPU) computing platform via the BlazeDEM3D-GPU code. We first perform an experimental validation of the code for mono-sized spherical and convex polyhedral shaped particles for lab-scale hoppers at three half angles using 3D printed polylactic acid material (PLA) particles. We found good agreement between the experimental, Meyrs and Sellers empirical relation and simulation discrete element method (DEM) discharge rates. We then simulate three larger square hoppers with varying half-angles to study the effect polydispersity and non-uniformity of particle shape have on the mass discharge rate. Again, good agreement between the DEM simulated mono-dispersed spherical particle systems and the Meyrs and Sellers empirical relation is obtained to verify the simulations. Finally we simulate an industrial sized silo for which we compare mono-dispersed spheres against mono-dispersed polyhedra using over a million polyhedral shaped particles. Finally, we briefly comment on the effect that the polydisperse nature of particle systems has on the loading of the supporting structure.

Computing with Non-convex Polyhedra on the GPU

We recently introduced Blaze-DEMGPU, a GPU based computing framework for convex polyhedral shaped particles (Govender et al. Appl. Math. Comp. 267, 810–829, 2015). The computing framework was validated against numerous industrial applications that include particulate discharge and estimating power draw for a ball mill in comminution applications. In this study we extend the computing capabilities of the convex polyhedral Blaze-DEMGPU computing platform to include non-convex polyhedral particles. We follow a similar philosophy to the well known clumping, clustering or fusing of spheres (Chong et al. Gran. Mat. 17, 377–387, 2015), but instead we fuse convex polyhedral particles. This allows for fused or super polyhedral particles that constitute effective physical properties for the fused particle e.g. the inertia tensor. The major benefit of fused polyhedral particles as opposed to clustered spherical particles is that the number of particles required to fuse fairly complex particle shapes is small. In addition, numerous decompositions exist to exactly decompose a non-convex particle in a number of convex particles. The main complexity of non-convex polyhedral particles is to resolve contact effectively and efficiently on the GPU. In this paper we outline our approach.

GPU DEM Simulations and Experimental Studies of Ball Milling Process for Various Particle Shapes

This work describes a comparative study on the milling process modelled by Discrete Element Method and lab-scale experiments. In particular, analogical complex granular media with spherical and polyhedral shaped particles have been used to support the development of Blaze-DEM GPU, which is graphical processor unit (GPU) based computing framework for convex polyhedral particle shapes. DEM simulations and experiments were performed for several filling rate, rotational speed and shaped particles. The experimental and DEM surface profiles are in good agreement that include avalanching, rolling, cascading and cataracting, The various flow regimes have been validated. The GPU allows for the computational efficient simulation of large numbers of particles or more complex polyhedral shaped particles. We consider the dodecahedron in this study. Therefore, GPU based DEM simulation conducted appropriately allows for large-scale industrial investigations to be conducted.

Study of Shear Behavior of Homogeneous and Heterogeneous Granular Materials by Experimentation and Numerical Simulation of Triaxial Test

This research aims at studying the shear behavior of homogeneous and heterogeneous granular materials by the triaxial test. The research work is performed on glass beads both in laboratory tests and by numerical simulations in DEM. The experimental tests are firstly performed on mono-disperses beads, then expanded to heterogeneous cases like bi-disperses mixtures. For numerical simulations, a cylindrical rigid wall boundary condition, based on Lame formula is implemented, and a series of procedures is proposed to simulate the conventional triaxial test in similar conditions to experimental tests. The numerical and experimental results are compared for both mono-disperses and bi-disperses cases. The numerical model can reproduce deviatoric curves satisfactorily in all experimental conditions.