Effect of particle sphericity on size segregation in rotating drums

• Particle sphericity strongly controls size segregation in rotating drums. • Decreasing sphericity suppresses percolation via geometric interlocking effects. • Lower sphericity increases dynamic angle of repose and granular temperature. • Segregation intensity shows a negative correlation with granular temperature. • Dynamic angle of repose serves as a robust macroscopic indicator of segregation. This study investigates how particle sphericity influences size-driven segregation and flow dynamics in binary granular mixtures using a quasi-two-dimensional rotating drum. In this study, the binary mixtures consisted of large white spherical particles and a second species of smaller black particles with systematically varied shapes. To isolate particle shape effects, four particle geometries with systematically controlled sphericities (φ = 0.806–1.0) and comparable particle volumes were examined over a range of rotational speeds from 3 to 5 rpm. The results demonstrate that decreasing sphericity significantly weakens size-induced segregation due to enhanced interlocking and reduced inter-particle voids, which suppress the percolation pathways typically exploited by smaller particles. Particles with lower sphericity also exhibit larger dynamic angles of repose (increasing by approximately 6–10°), higher average velocities (up to ∼28%), and elevated granular temperatures, indicating stronger energy dissipation and more vigorous agitation within the flowing layer. Increasing rotational speed further amplifies these dynamic effects. Importantly, the final segregation intensity exhibits a negative correlation with both average granular temperature and dynamic angle of repose across all particle shapes and speeds, demonstrating that these two macroscopic flow descriptors provide robust, experimentally accessible indicators governing segregation behavior. These findings provide direct experimental evidence of how controlled particle shape variation modifies segregation mechanisms in rotating granular flows.