A DEM Study on the Timescale of Particle Size Segregation in Granular Flow

Granular materials are commonly encountered in both natural environments and industrial applications. When provided with sufficient energy, these materials exhibit fluidlike behavior, introducing complex challenges in predicting their flow dynamics. One such phenomenon is particle size segregation, in which particles separate based on size, often leading to operational inefficiencies in industry and contributing to geophysical hazards in nature. This study employs the discrete-element method (DEM) to investigate particle size segregation in dry granular flows. Three key parameters were varied: small particle concentration (10%–90%), particle size ratio (1.5–3.5), and the angle of inclination ( 24∘−30∘). Results indicate that segregation occurs more rapidly at steeper angles, while the extent of segregation is maximized at lower angles. Furthermore, variations in particle concentration influence the shear profile of the flow, thereby affecting segregation dynamics. By tracking percolation paths of particles, a linear relationship is observed between maximum percolation velocity and local shear rate. Based on this, an empirical scaling law is proposed for the segregation timescale, incorporating local concentration and shear. This relation aligns with both present findings and prior studies, offering a predictive framework for early-stage granular segregation dynamics.