Modelling of granular mixtures placing. Comparison between a 3D full-digital model and a 3D semi-digital model

This paper concerns a comparative study between a 3D full-digital and a 3D semi-digital model with the aim to represent the gravitational placing of granular mixtures with a very high number of particles. Both models use a completely digitized volume and a similar filling procedure considering ramdom local rules for the particles displacements and taking into account only steric repulsion between particles. The full-digital model is based on the digitization of the particles and their displacements. The semi-digital model takes into account the curvature of particlesʹs surface and displacements of particles depend on real numbers instead of integers. Mono-sized spherical particles systems in homothetic conditions were firstly studied with both models. It is shown that the full digital model is very sensitive to the size of particles. Random loose packing of mono-sized systems can be stimulated correctly only when the radius of particles is equal or higher that 4 pixels. On the contrary, the semi-digital model allows a good representation of the random loose packing of mono-sized spherical particles sysytems independently of the particles radius. The comparison between the two models also concerns the study of binary mixtures with varying proportion of small particles