Pebble bed structures in the vicinity of concave and convex walls

Abstract Computed tomography experiments were performed with mostly spherical particles in containers with concave, plane and convex walls. Regular pebble packings exist also close to convex cylindrical walls even if the cylinder-to-pebble diameter ratio is about 1, characteristic of thermocouples within the pebble bed. A model for arbitrary container shapes is proposed which predicts the inner packing factor based on the known total packing factor. With increasing vibration efficiency the total packing factor rises because the zones with structured packing increase. Depending on container dimensions, a structured packing can occur in the total pebble bed. Large packing factors are desirable, however, these pebble beds can probably no longer be considered as isotropic with respect to thermo-mechanic properties.