Over the past several years, IFPRI-supported work at Duke has focused on understanding jaming and flow properties in a quasi-2D hopper by using photoelastic particles. Two final goals of the proposed work were
1) to extend studies using cohesionless photoelastic particles to similarparticles, but with cohesive interactions, and
2) to studies of three dimensional systems. During the final year of this project, we have addressed the goal of using cohesive particlesby carrying out i) studies of particles with cohesion and ii) studiesof the stress response of systems of agglomerate particles, which have theproperty that they can break. We have
3) carried out additional studies of hopper flow for cohesionless photoelastic particles, where we have used synchronized high speed video imaging for both particletracking and photoelastic imaging. The goals of 3) are to understand the coupling between force chains (as a measure of stresses), flow velocity, and density. A key rationale of this last set of studies is to understand the relation between the various granular states that occur for hoppers: flowing and jammed, and to understand whether shear jammed states (recently discovered at Duke) are in fact the same states that occur for jamming of a hopper. We have also developed a new approach for studying fully 3D granular systems at the particle scale, which includes the measurement of inter-particle forces and particle motion. This report provides information on the last year’s work, as well as a highlights of previous results.
IFPRI support has led to the Ph.D. of Junyao Tang, now employed in industry.Two additional students, Audrey Melville, and Yiqiu Zhao, have worked on this project in the past year.