Clogging of granular material in vertical pipes discharged at constant velocity

Abstract

We report an experimental study on the flow of spherical particles through a vertical pipe discharged at constant velocity by means of a conveyor belt placed at the bottom. For a pipe diameter 3.67 times the diameter of the particles, we observe the development of hanging arches that stop the flow as they are able to support the weight of the particles above them. We find that the distribution of times that it takes until a stable clog develops, decays exponentially. This is compatible with a clogging probability that remains constant during the discharge. We also observe that the probability of clogging along the pipe decreases with the height, i.e. most of the clogs are developed near the bottom. This spatial dependence may be attributed to different pressure values within the pipe which might also be related to a spontaneous development of an helical structure of the grains inside the pipe.

Clogging in two-dimensions: effect of particle shape

“…This is due to the fact that squares can pile up with a rather high internal angle in comparison with other polygons. This can build a very narrow vertical channel that can be clogged with high probability at many dierent heights, as it has been shown in vertical pipe experiments [34]. This eect leads to a very spread distribution in the arch vertical position for squares as it can be observed in the notched box plot of figure 8(b).…”