Intruder-induced asymmetry in compartmentalized granular gases

The clustering behavior of a compartmentalized monodisperse granular gas with the addition of one heavy intruding particle is investigated experimentally. Depending on the number of particles, the presence of a heavy intruder leads to three population states: a homogeneous state, an expelled clustering state, and a fully clustering state. These states are found to be consistent with the clustering of a purely monodisperse granular gas in an asymmetric compartmentalized structure. We obtain an exact relation between the size of an intruder and the elevation of the compartment bottom. This relation quantifies the particle-expelling ability of a heavy intruder, and suggests that the one-intruder system is a type of asymmetric system with an intruder-size-related asymmetrical index ξ. Under the framework of the flux model, a ξ-associated Ξ function is proposed to quantitatively reproduce the experimental results.