  Granular flow in a silo demonstrates multiple nonlocal rheological phenomena
due to the finite size of grains. We solve the Nonlocal Granular Fluidity (NGF)
continuum model in quasi-2D silo geometries and evaluate its ability to predict
these nonlocal effects, including flow spreading and, importantly, clogging
(arrest) when the opening is small enough. The model is augmented to include a
free-separation criterion and is implemented numerically with an extension of
the trans-phase granular flow solver described in arXiv:1411.5447, to produce
full-field solutions. The implementation is validated against analytical
results of the model in the inclined chute geometry, such as the solution for
the $H_{\mathrm{stop}}$ curve for size-dependent flow arrest, and the velocity
profile as a function of layer height. We then implement the model in the silo
geometry and vary the apparent grain size. The model predicts a jamming
criterion when the opening competes with the scale of the mean grain size,
which agrees with previous experimental studies, marking the first time to our
knowledge that silo jamming has been achieved with a continuum model. For
larger openings, the flow within the silo obtains a diffusive characteristic
whose spread depends on the model's nonlocal amplitude and the mean grain size.
The numerical tests are controlled for grid effects and a comparison study of
coarse vs refined numerical simulations shows agreement in the pressure field,
the shape of the arch in a jammed silo configuration, and the velocity field in
a flowing configuration.
