Clogging of Dry Granular Material Through Particle Arrays in 3D

When dry granular materials such as sand and gravel flow through an opening, they can sometimes get clogged. Clogging occurs because a few particles form an arch/bridge that acts as a dam and does not allow the rest of the material to flow through. Our study uses LAMMPS (lammps.org) to study the clogging of grains poured under gravity through a sieve formed by a single layer of rigid particles arranged in a simple cubic lattice. We first pour in batches of monodisperse particles smaller than the gaps/voids created by four adjacent sieve particles. These smaller particles interact with one other and with the particles in the sieve via Hertzian contact interactions. We find that the time for the system to be fully clogged decreases when each poured batch contains a larger number of particles. At the same time, the average root mean squared displacement of particles near the sieve approaches zero with each subsequent pour, and the clogged arch-like structures immediately above the sieve are dense and stable. We report on the clogging profiles for bidisperse/polydisperse particle mixtures to study the effects of clogging on separating two different-sized particles. We also find that in some cases, particles with a low visco-elastic damping constant but a higher coefficient of friction have a better flow efficiency. This could have significant implications for industries that depend on particle separation.