This award supports experimental and computational studies of the flow of granular materials composed of mixtures of particles. The project will investigate the surprising observation that adding a small number of needle-like particles in a granular material composed of spherical particles significantly increases the ability of the material to flow. For very small particles, the investigators hypothesize that the needles and spheres stick together in a way that results in an effective particle shape and size that enables the material to flow more easily. For larger particles less likely to adhere, other lubrication mechanisms are suspected. A series of experiments will be conducted to show how the particle size and the mixture ratio affects flow characteristics. The experiments will be complemented by numerical simulations that can predict the arrangements of particles and correlate particle arrangements with flow behavior in well-defined model flows. The project will provide an environment for graduate and undergraduate students to participate in the research.
This project studies the flow and shear of mixtures of particles consisting of spherical and irregularly-shaped particles. Experiments will be conducted with canonical geometries, such as hoppers, cylindrical column collapse, and annular-Couette shear, to study the flow behavior as functions of particles size and mixture ratio. The experiments will tie together several quantities currently used to quantify flow, including the static and dynamic angles of repose, dynamic deflection modulus and flowability index. Computer simulations will study shear in dense systems of rods and mixtures of rods and spheres to reveal the fundamental mechanisms for enhanced flow whether it is changes in the effective morphology or segregation-induced lubrication.
