Compaction of highly porous granular matter by impacts on a hard wall

Abstract

Using a granular-mechanics code, we study the impact of a highly porous granular body on a hard wall. The projectile consists of monodisperse adhesive micrometer-sized silica grains. For the impact velocities studied, v<0.5m/s, the sample does not fragment, but is compacted. We find that the compaction is proportional to the impact speed. The proportionality constant increases with decreasing porosity. However, the compaction is inhomogeneous and decreases with distance from the target. A compaction wave runs through the aggregate; it slows down while the compaction becomes less efficient.

A granular mechanics model study of the influence of non-spherical shape on aggregate collisions

“…The effects of changes in the surface energy—and hence the grain adhesion—on aggregate collisions has to our knowledge not been studied with comparable care. However, we mention that an increased leads to a quicker stopping of the aggregates 35 and a stronger material compaction 36 ; hence it can be expected to lead to less fragmentation in aggregate collisions, even though this aspect does not seem to have been investigated systematically.…”