Impact of an obstacle on granular flow through apertures

It is not uncommon to observe the flow of discrete entities through narrow openings. Examples include transporting granular media through outlets in hoppers. Developing a robust mechanism to regulate granular flow through apertures without clogging is a central point of various studies conducted over decades. Previous works report that placing an obstacle just above the outlet reduces jamming and improves the flow rate. However, a comprehensive understanding of the dynamics of granular flow in these scenarios remains elusive. In this study, we examine the influence of an obstacle on granular kinematics in a quasi-two-dimensional silo using discrete element computations. The aperture size is large enough to ensure a continuous flow. We vary the frictional characteristics of the walls along the thickness, keeping them either smooth or rough. The vertical placement of the obstacle at which the flow rate becomes equal to the no-obstacle scenario depends on the frictional nature of the walls. In light of this, we show that the velocity and density fields at the exit exhibit contrasting behaviour.