Jamming transition in Couette shear*

We study the jamming transition with a novel Couette experimental apparatus, which allows us to shear an ideal 2D photoelastic granular system. The photoelastic particles are suspended in a density matched fluid, so that there is no basal friction. We simultaneously record the particle positions and photoelastic response over a range of shear rates. The photoelastic data provide grain scale forces on the particles. The macroscale shear stress is obtained by a torque sensor. We study the correlation between the granular scale pressure from the photoelasic response, and macroscale shear stress during the shear jamming transition. We also determine the coarse-grained strain field, which shows novel convective flow over large strains.