  Nonlocal rheologies allow for the modeling of granular flows from the
creeping to intermediate flow regimes, using a small number of parameters. In
this paper, we report on experiments testing how particle properties affect
model parameters, using particles of three different shapes (circles, ellipses,
and pentagons) and three different materials, including one which allows for
measurements of stresses via photoelasticity. Our experiments are performed on
a quasi-2D annular shear cell with a rotating inner wall and a fixed outer
wall. Each type of particle is found to exhibit flows which are well-fit by
nonlocal rheology, with each particle having a distinct triad of the local,
nonlocal, and frictional parameters. While the local parameter b is always
approximately unity, the nonlocal parameter A depends sensitively on both the
particle shape and material. The critical stress ratio mu_s, above which
Coulomb failure occurs, varies for particles with the same material but
different shapes, indicating that geometric friction can dominate over material
friction.
