Avoiding clogs: The shape of arches and their stability against vibrations

Abstract

Abstract. A distinctive feature of discrete solids is their ability to form arches. These mechanically stable structures alter the isotropy of granular packings and can arrest the motion of grains when, for example, they flow through a bottleneck. Breaking arches can be achieved by means of an external vibration, which effectively eliminates clogging. Indeed, these phenomena and procedures are quite common in industrial applications. Nevertheless, there are not rigorous, well founded criteria to determine the most efficient way to break arches and restore the flow of grains. This happens in part because it is not known which are the relevant characteristics that boost the arch strength. In the experiment presented here, we have carried out a statistical analysis of the arches that block the exit orifice at the bottom of a two dimensional silo, and described their geometrical properties. We then submit the silo to an external vibration. We find that the larger the outlet size, the weaker the arches that clog it. This dependence is just the outcome of a more complicated process that involves geometrical defects in the arch. The defects are quantitatively defined in terms of contact angles and we show that this is a key factor regarding the endurance of arches.

Increasing granular flow rate with obstructions

“…Therefore, in order to get reliable and reproducible flow rates, we decided to perturb the particles just sufficiently to prevent extended periods of clogging which thereby affect flow rates. As described by Garcimartin et al [11], the problem of clogging can effectively be eliminated by applying external vibrations. In a similar way, we use the technique of 'shaking'.…”

DEM Study on the effect of particle‐size distribution on jamming in a 3D conical hopper

“…To avoid jamming, one effective way is by vibration . Janda et al observed that the discharge rate significantly increased with the vibration amplitude.…”

“…Mankoc et al concluded that vibration increased the size of the avalanches (i.e., amount of particles discharged between two continuous jams) markedly. Garcimartín et al found that larger outlet orifice sizes weakened the arches that clog due to the external vibration. Mondal and Sharma observed via simulations that, for a small ratio of orifice diameter to particle diameter, having two adjacent outlets averts the jamming caused by a single outlet.…”

An investigation into the impact of particle properties on flow behaviors

“…Pournin et al [98] obtained the function for median jamming diameter (which is the hopper opening diameter for 0.5 of jamming probability) and particle diameter by investigating the effect of friction and boundary condition, and illustrated the jamming formation comes after the concentric particle rings. To avoid jamming, vibration is one of the most effective ways [28,87,99]. Janda et al [87] presented discharge behavior with the vibration and pointed out that the discharge rate increased with the vibration amplitude significantly.…”

“…To avoid jamming, one effective way is by vibration [28,87,99]. Janda et al [87] observed that the discharge rate significantly increased with the vibration amplitude.…”