Capturing the dynamics of a two orifice silo with the {\mu}(I) model and extensions

Granular material in a silo with two openings can display a `flow rate dip', where a non-monotonic relationship between flow rate and orifice separation occurs. In this paper we study continuum modelling of the silo with two openings. We find that the \(\mu(I)\) rheology can capture the flow rate dip if physically relevant friction parameters are used. We also extend the model by accounting for wall friction, dilatancy, and non-local effects. We find that accounting for the wall friction using a Hele-Shaw model better replicates the qualitative characteristics of the flow rate dip seen in experimental data, while dilatancy and non-local effects have very little effect on the qualitative characteristics of the mass flow rate dip. However, we find that all three of these factors have a significant impact on the mass flow rate, indicating that a continuum model which accurately predicts flow rate will need to account for these effects.