Analysis of particle motion in a radially segregating binary granular mixture

Abstract

Mixtures of granular materials differing in density or size tend to segregate when subjected to vibration or shear. This is a challenge if the application requires that the material must remain mixed. We perform a DEM simulation of a shear-driven size-based radial segregation in a rotating drum. Previous studies are mostly on pattern formation at the "macroscopic" scale. The present work focuses on the evolution of the characteristics at the "microscopic" scale, particularly on the periodicity and roughness of the motion of the individual grains as segregation progresses. The periodicity of the tracers' trajectories generally shifts to higher frequencies while the spectra of the tracers' velocities have no characteristic peaks. The mean value of the fractal dimension of the large tracers' phase space plot dips at the transition stage while for the small tracers, it increases in later segregation stages. The spectra of the trajectory and the fractal dimension of the phase space have potential use for characterizing particle motion during radial segregation. However, more studies are needed and we recommend considering more tracers, smaller time steps, higher size ratio, and different drum speeds.