Packing and flow profiles of soft grains in 3D silos reconstructed with X-ray computed tomography

High-speed x-ray tomography of silo discharge

“…These experiments demonstrated qualitative differences of the discharge dynamics through narrow orifices as compared to rigid spheres. For 3D bins, similarly distinct flow profiles of the rigid spheres and hydrogel spheres were confirmed qualitatively by means of XR-CT [5]. One peculiarity of the flow of hydrogel beads was that both in 2D and 3D containers, there were no stagnant zones.…”

“…For a large variety of hard, frictional spherical grains, it has been shown that the diameter of the opening must be larger than approximately five times the particle diameter to avoid clogs [1,2]. When the particles are soft and slippery, they flow through much narrower outlets without clogging [3][4][5]. For non-spherical particles, shape parameters influence the discharge statistics [6,7].…”

“…with the determination of flow rates [1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], the statistics of clogging [2,[23][24][25][26][27][28][29][30], the influences of obstacles near the orifice on the flow rates [31,32], and the role of gravity and embedding fluids [33][34][35]. The role of softness has been considered only recently in a few papers [3][4][5].…”

“…Conventional 3D XR-CT typically requires seconds to record single images, so it can only be applied to static granular ensembles, viz. clogged states of a silo [5,6,47], stepwise intrusion of a punch in a granular bed [48,49], stepwise compression [50,51] and others.…”

“…In silos, for example, one may create pulsating flow by opening the orifice only for short intervals. XR-CT images of silo discharge, for example, were recorded during the stopped phases with either the orifice closed [5] or in a clogged state [6].…”