Our three scientific Work Packages considered deformable, irregular and cohesive granular materials, and for each of these types of grains we have developed new scientific perspectives, sometimes combining the work from different work packages. We have advanced calibration methods for granular materials to better characterize these materials both on their mechanical behavior and their microstructural evolution. We have advanced several numerical methods to better simulate soft particles flows, and particle flows of anisometric grains. We have been able to image the swelling of soft, deformable, anisometric couscous particles in 3D with both X-ray tomography and neutron tomography, providing the highest detail so far of a granular process that involves soft, sticky particles. These results have even been combined with NMR confirmation of hydration levels, which is an industry first.
We have extensively studied deformable, irregular and cohesive granular flows in silos and hoppers, revealing new important couplings between the frictional and elastic behavior of granular materials, the role of deformability and shape in classic equations such as the Hagen-Beverloo equation. We have additionally characterized frictional and adhesive contacts in deformable and irregular flows and have cross-calibrated numerical particle models on experimental results for different flow geometries, including more classic floe geometries such as a Schulze ring-shear tester. We have developed novel discrete element method code to simulate the continuous and oscillatory flow behavior of deformable particles, the interactions among them and their coarse-grained mechanical response.
Scientifically, the network has studied a very broad array of granular samples, ranging from ceramic particles used in ceramic tile production, to rice grains, macaroni particles, mustard seeds, couscous grains and hydrogel beads and an array of model shapes including non-convex tripods and hexapods. We have developed custom flow geometries for slow flow imaging in special rheometric configurations, allowing for full characterization of flow behavior. The flow geometries are suitable for slow and fast flow imaging. In general, we have used an extremely wide range of flow imaging modalities: slow and high speed X-ray, MRI, high speed imaging and neutron tomography. We have also combined some of these imaging modalities. We have used and developed various numerical methods to study granular materials, including hybrid GPU-CPU frameworks. An extensive calibration workflow scheme is also developed that works together with industry-standard discrete element method simulation codes.
Summarizing, the scientific work has resulted in many new perspectives on hopper flow physics as relevant for industrial practice, new three dimensional flow rules for slow flows of non-convex particles shapes, a new understanding of the cohesive nature of ceramic particles, the establishment of new microscopic pictures behind the role of rotations of grains in geophysical context, new modeling perspectives for the elastic behavior of soft particle packings among others.
