Flow behaviour of granular materials: modelling wall adhesion and its impact on grain segregation

Granular assemblies, composed of large collections of discrete, macroscopic particles, exhibit complex and often unpredictable behaviours during flow. For instance, discharge of granular materials from a hopper can result in particles segregating by size, and the role of wall adhesion in this process remains underexplored. This study uses Discrete Element Modelling (DEM) to examine how wall adhesion affects particle segregation and mound formation on discharge. A bin-based method from [4] is employed to assess segregation under gravity in mass flow and funnel flow geometries. Segregation in both geometries is primarily driven by percolation during loading. In mass flow, wall adhesion primarily affects finer particles at lower regions, influencing their initial flow patterns, while its impact on larger particles increases with height. In funnel flow, adhesion influences larger particles throughout the system, with strong adhesion values (>0.025 J/m²) impeding finer particle flow at higher levels, ultimately reversing initial segregation trends. This results in layered segregation across different flow phases, producing distinct stratified layers in the discharge mound.