This project investigates a class of granular materials that are geometrically cohesive, e.g. a collective pile of particles that resists tensile forces. Examples of geometrically cohesive granular materials (GCGM) include long, thin rods (e.g. haystacks) and concave-shaped particles (semi-circles or U-shaped staples). These materials present a rich opportunity for basic research as well as new practical applications where structural rigidity, lightweight, and porosity are desired.
Computer simulations and experiments for a variety of particle shapes - rods, semi-circles, and U-shaped staples - will be carried out to provide a better micro and macroscopic understanding of how particle shape affects fluidization and solidification in GCGM. Experiments previously carried out to characterize spherical granular media?basic rheology, tumbling, collapse, and flow ? will be repeated for the above complex-shaped particles. Numerical simulations using the Discrete Element Method will be used to probe the particle-level mechanism by which geometric cohesion occurs. New parallelization techniques involving graphics processing units (GPUs) will be developed for simulating thousands of particles. These experimental and computational studies will be used to explore the possible universality in geometric cohesion, the scaling of critical lengths, and the fundamental mechanism by which this cohesion occurs.
This work will lead to increased understanding of granular materials consisting of complex shaped particles, a common occurrence in many industrial processes. The project also initiates collaboration between two institutions: a primarily undergraduate institute, Rochester Institute of Technology, and an R1 research university, University of Rochester. The collaboration will engage undergraduate and graduate students in a rich educational experience that emphasizes communication between experimentalists and computational researchers. Simulations and table-top experiments will allow undergraduates to engage in cutting edge research at both institutions.