Effect of vibration conditions on packing structures of trilobed particles

Abstract

Packing behaviors of non-spherical particles are generally far more complex than those of spherical particles. Trilobes are widely adopted as supports for catalyst in the field of chemical engineering, and thus their packing behaviors subjected to continuous vertical vibration are numerically investigated by discrete element method in this article. Geometrically exact contact detection algorithm between sphero-cylinders and multi-sphere method are coupled to describe the shape and motion of trilobed particles. It is found that there exist two preferential orientations, which are quite different from the phenomenon of sphero-cylinders. Ordered clusters of different orientations co-exist in the heterogeneous granular bed with obvious phase junctures. The initial stage of crystallization process can be explained by the nucleation growth mechanism. With the growth of the nuclei, distances between small ordered clusters decrease gradually and those ones with identical orientation can eventually get coalesced to form a larger cluster. Moreover, novel sunflower-shaped clusters composed of trilobes of different orientations are observed under vibrations of low amplitudes and high frequencies. In the meanwhile, no consistent relationship between packing densities and packing structures can be found for the dense packing of trilobes. Therefore, other packing parameters more sensitive to the local structures should be analyzed together with the overall packing densities to comprehensively understand the packing behaviors of non-spherical particles.