Obstacle-Induced Shape Transformations of Granular Arches in a 3D Silo

The formation of stable arches leads to intermittent clogging during discharge from hoppers. In recent work (Sinha et al. [1]) we have shown that a slender rod inserted into the flow can suppress clogging, with purely geometric considerations determining the optimal height of a rod for a given diameter. Building on that work, we now analyze the geometry of the arch through imaging, and find direct evidence that the rod participates in the clogging arch when optimally located. The rod modifies the shape of the arch, making it both asymmetric and variable in position. The shape of the arch also signals the best choice of rod diameter to minimize clogging.