Compaction of a two-dimensional system of composite spherical particles under the influence of self-gravitation: Between lock-and-key model and Tetris-structure

Abstract

Abstract A self-gravity ofspherical granular particles in the two-dimensional system is simulated. Some of the spherical particles are bonded through a spring force to form composite particles. These spherical and composite particles are attracted to each other due to gravitational force and prevented from collapse into a single point by the normal force. A previous study reported that a two-dimensional monodispersed system will form a hexagonal close-packed (HCP) configuration. In this work, it will be perturbed by some of the composite particles that could have HCP form, simple cubic (SC) form, or a mix of SC-HCP (MSH) form. These forms can be categorized into SC family (□, I, L, T, F, H, E), HCP family (Δ, □, V, X), and MSH family (⌂, K, M, W, N, Z), that can be compacted to maximum contactopy through lock-and-key mechanism (KL). The compaction of some forms from the SC family is similar to the Tetris game, where the structure should be compacted before it could be eliminated in the game. In this work, not all forms from the three families are simulated. The particles in general tend to form a final configuration with the most compact form and the composite particles seems also to influence their surrounding particles to construct the configuration.