Modulation of segregation pattern inversion induced by the initial packing mode of binary granular mixtures in a vertically vibrating rectangular container

This study explores the modulation of segregation inversion induced by the initial packing mode of binary granular mixtures in a vertically vibrating rectangular container. A binary system composed of size-matched brass particles (heavy) and plastic particles (light) was employed to probe the density-driven segregation. Experimental and simulational results demonstrate that the inversion time from RBNE to BNE critically depends on initial packing mode: the random-mixed mode exhibits the longest inversion duration, succeeded by the RBNE packing mode. In contrast, inclined RBNE and side-by-side packing modes exhibit progressively faster segregation dynamics. Spatiotemporal analysis of granular temperature evolution reveals that, compared to the RBNE packing mode, the inclined RBNE packing mode promotes more efficient vertical-to-horizontal energy transfer. The higher horizontal granular temperature accelerates localized packing fraction reduction, amplifies buoyancy-driven forces, and enhances the downward migration of heavy particles coupled with the upward motion of light particles. Additionally, particle aggregation triggers cooperative clustering behavior, which further accelerates the RBNE-BNE inversion.