Jamming and critical outlet size in the discharge of a two-dimensional silo

Abstract

-We present an experimental study of jamming in the discharge of grains through an opening in a two-dimensional silo. For a wide range of outlet sizes, we obtain the size distribution of avalanche defined as the number of grains that fall between two consecutive jams. From these distributions, we obtain the probability that the silo jams before N particles pass through the orifice. Then a simple model of arch formation is proposed that predicts the shape of the jamming probability function and reveals that it does not exist a critical size of the orifice above which there is not jamming.

Silo Clogging Reduction by the Presence of an Obstacle

“…1 we show that, regardless of the obstacle position, the avalanche size distribution displays an exponential decay as it was previously found for the silo without obstacle [4]. The difference between the distributions for different values of h, is the mean avalanche size hsi which is indeed related to the probability that a particle clogs the outlet (1 À p) by the equation 1 À p ¼ 1 À hsi=ðhsi þ 1Þ [6].…”

“…Since To and co-workers proposed that the clogging in the discharge of a silo is caused by the formation of arches whose shape can be explained through a restricted random walk model [1], numerous researches have been devoted to this phenomenon [4][5][6][7][8][9][10]. From these works, it is rather well known that the main variable that comes into play in the clogging process of spherical particles is the ratio between the outlet size and the diameter of grains.…”

“…Indeed, for three-dimensional silos, it seems that there is a critical outlet size above which clogging is not possible [4]. For the two-dimensional case, the existence or not of such a critical size remains unresolved [5,6]. In both cases (2D and 3D silos), for a given outlet size, the sizes of the avalanches s (measured as the number of particles that flow out of the silo before an arch blocks it) display an exponential distribution.…”

“…week ending 30 DECEMBER 2011 one described in [6] with the only difference being that a circular obstacle has been placed above the outlet (Fig. 2).…”

Force analysis of clogging arches in a silo

“…In all these systems clogging arches withstand the weight of the particles above them just as architectural arches do. For the case of silos, a link has been sought between the properties of the arches and the clogging probability [13,14,22,23]. Although the relationship is not fully understood, the knowledge about the properties of these assemblies has been notably improved.…”