2d Shear of Granular Annular Sector Particles (ASPs)

We study the shear of granular annular sector particles (ASPs), open semi-circular rings that have previously been studied at colloidal scales. ASPs can be characterized by two dimensionless numbers: the subtended opening angle and the ratio of inner and outer radii. We place granular ASPs in an annular-planar Couette shear cell and visualize the entire 360° with six cameras. Particle tracking software identifies the position and orientation of each ASP and enables measurement of large-scale motion and particle-particle interactions. ASPs can entangle to form dimers, trimers and other structures and we measure the distribution, creation and annihilation of these structures. Dimers can be characterized by the dot product of constituent ASP orientations. I will describe our initial experiments and compare with collaborative experiments in avalanching geometries.