Competition in the Segregation Mechanism of Granular Flow within a 2D Rotating Drum Based on Magnetic Positioning Technology

Particle segregation is an inevitable stage in the disaster processes of geological hazards such as debris flows. Influenced by multiple factors including size, density, and macroscopic flow velocity, varying degrees of competition exist within its microscopic motion mechanisms. To precisely observe these mechanisms in granular flow, this paper designs a high-precision magnetic array positioning system based on magnetic dipole theory, enabling dynamic tracking of magnetic bead trajectories within a three-dimensional system. By integrating particle swarm optimization and gradient-based local optimization algorithms, the system achieves a dynamic positioning accuracy ranging from ± 0.5 mm to ± 2 mm and improves trajectory continuity to 99%, accomplishing complete reconstruction of magnetic bead paths in a quasi-two-dimensional rotating drum. The Froude number is applied to quantify the competition among segregation mechanisms governed by inertial, gravitational, and contact forces across different rotational speed stages. Trajectory analysis reveals that differences in density and flow velocity alter the motion mechanisms of intruder particles. Specifically, the motion of intruder particles evolves through three characteristic phases with varying Froude numbers: gravity-dominated, collision-diffusion transition, and centrifugal diffusion. Each phase exhibits distinct dominant forces in the flow field and particle kinematic properties, showing varying trends influenced by surrounding particles of different densities. These findings provide both data support and mechanistic explanations for research on the disaster mechanisms and prediction of geological hazards such as landslides and debris flows.