Modeling silo jamming with a nonlocal continuum model

The fact that a silo or hopper jams when the opening size is reduced below a critical value defies most, if not all, local continuum models of granular media. Nonlocal models, which account for the affect of a finite grain size within the rheology, have the unique ability among continuum apporaches to address this issue. Previously, the Nonlocal Granular Fluidity (NGF) model has shown the ability to capture an analogous situation, the apparent strengthening due to thin-ness that causes thin layers of grains to require more tilt to flow down a rough incline than thicker layers; i.e. the Hstop effect. In this talk, we will show the same model can also capture the apparent strengthening due to thin-ness that causes silos and hoppers to jam when the nozzle size is smaller than a critical value. To show this, the model is implemented in a set of silo geometries with a meshless solver. We show the model predicts a jamming criterion that is in the proper range for simple grains, and explore the form of the flow/no-flow phase diagram it predicts.