The kinetically-constrained Kob-Andersen model has proven to be efficient in describing granular matter close to jamming. The model allows us to calculate numerically the current of particles propagating through a lattice, the particle density and even evaluate spatial correlations between the particles and the effect of these correlations on measurable parameters such as current and density. This simple model also allows us to analytically predict the probability of the system to be in a stuck state or to detect particles that will never be able to move.

We simulate the movement of granular material through an orifice subjected to a constant gravitational field. We study the behavior as a function of orifice size, initial conditions, system size, particle density and the acceleration of gravity. To that end, we constructed a computationally efficient Monte-Carlo simulation, which implements a rejection-free algorithm.

We consider a square lattice with and without an orifice, with periodic boundary conditions in the direction of the gravitational field and either rigid walls or periodic boundary conditions in the transverse direction. We compare different ways to implement a gravitational field in the Kob-Andersen model and study the current and density spatial profiles as well as correlations that develop in the system.