Granular flows: effects of grain shape and surface friction (Creating Granular Materials Experts by Developing Experimental Calibrations for Computational Methods).

Experimental investigations will be performed for a better understanding of granular flows: shear flows and hopper flows. We will focus on the role of grain shape and surface friction in the flow dynamics. The project is part of a large scale effort (EU Marie-Curie ITN) entitled “Creating Granular Materials Experts by Developing Experimental Calibrations for Computational Methods” (CALIPER) which is coordinated by Dr. Joshua Dijksman at Wageningen University and involves several European laboratories. We will use sophisticated experimental techniques, such as high speed imaging, X-ray computed tomography, Magnetic Resonance Imaging (MRI), or high speed (1000fps+) X-ray tomography. Part of the experimental work will be done in close collaboration with the Nonlinear Dynamics group at Magdeburg University (Germany). The experimental data will be used as benchmark for calibrating numerical models developed at University of Navarra (Pamplona, Spain) or by DCS Computing (Linz, Austria). With all groups, longstanding relations have been built, that in some cases go back 10+ years. We will study at a microscopic level, how elongated particles rotate and get oriented in a shear flow due to the interaction with their neigbours. This affects the effective friction of the granular material, i.e. its resistance against shear. We will also investigate the role of interparticle friction in hopper flows, by analyzing flow and clogging of mixtures of particles with high and low surface friction. Further hopper flow experiments will be done with particles of lower symmetry e.g. rods with one of their ends sharpened.