Simulation of random mixed packing of different density particles

This paper presents the effects of density difference onthe three-dimensional (3D) distribution of random mixed packing. Therandom mixed packing dynamics of particles of two differentdensities are simulated. The initial state is homogeneous, but thefinal packing state is inhomogeneous. The segregation phenomenon(inhomogeneous distribution) is also observed. In the final state,the top layers are composed of mostly light particles. The severallayers beneath the top contain more heavy particles than lightparticles. At the bottom, they also contain more heavy particlesthan light particles. Furthermore, at both the top and the bottom,particle clustering is observed. The current study also analyses thecause of this inhomogeneity in detail. The main cause of thisphenomenon is the velocity difference after collision of these twotypes of particles induced by the density difference. The presentstudy reveals that even if particles were perfectly mixed, thepacking process would lead to the final inhomogeneous mixture. Itsuggests that special treatment may be required to get the truehomogeneous packing.