Characterisation of the effects of particle shape using a normalised contact eccentricity

In discrete element modelling it is quite common to employ rolling friction models to mimic the effects of particle shape. This paper presents an investigation of the mechanisms at play when using this technique and compares the behaviour of a rolling friction model with various non-spherical particle systems. The motivation behind this work revolves around forming a theoretical framework behind the selection of a coefficient of rolling friction. As a part of this study, we describe an approach where the normalised average contact eccentricity of non-spherical particles (in this case multispheres) is used to characterise the effects of shape. This description is found to capture some aspects of material behaviour reasonably well. When compared to the behaviour of a common rolling friction model, it was found that similar behaviour could be approximated by spheres with a coefficient of rolling friction equal to one half of the normalised eccentricity of non-spherical material. This is approximately in-line with previous studies involving 2D polyhedral particles (Estrada et al. in Phys Rev E 84:011306, 2011)