The principal aim is to characterise the flow properties of dense granular systems. In particular, the influence of different particle-shape representation techniques in the Discrete Element Method (DEM) is assessed. Additionally, experiments in a silo centrifuge device to determine the bulk response of granular assemblies under realistic stress states are being carried out. This work is part of T-MAPPP (Training in Multiscale Analysis of multi-Phase Particulate Processes), an FP7 Marie Curie Initial Training Network (https://www.t-mappp.eu).
Particle-scale characteristics govern the behaviour of particulate materials at the macroscale. An important factor that dominates the interaction of individual particles is shape, which generates particle interlocking. This affects the contact force network and the particle motion which lead to change in rheology, as well as stress distribution in the granular system. We consider Discrete Element Method (DEM) simulations, together with direct shear and silo discharge experimental tests, to determine the influence of particle shape on the mechanical response of granular assemblies at the micro- and macro-scales.
Spheres are usually used for describing particle shape in DEM, due to simplicity and computational cost. In reality, however, particles are mostly of irregular shapes, which increases degree of inter-particle interlocking among the particles. Controlling rotation (i.e., use of rolling resistance models) can overcome the lack of geometric interlocking for the spheres. A part of this project focused on the effects of two rolling resistance models on both packing and discharge characteristics of spherical particles. The results suggested that, in case of silo discharge, use of rolling resistance models can partially follow the influences of non-spherical shape particles.
There exist other approaches to simulate shape. Two widely used approaches, “Multi-spheres” and “Superquadrics”, are employed and the influence of changing particle surface and edge complexities on the micro- and macro- scale response is assessed for several test cases [1].
References
[1]B. Soltanbeigi, A. Podlozhnyuk, S.-A. Papanicolopulos, C. Kloss, S. Pirker, and J. Y. Ooi. DEM study of mechanical characteristics of multi-spherical and superquadric particles at micro and macro scales. Powder Technology, 329:288 – 303, 2018.
