Particle angularity controls granular flow under vibration

Granular materials exhibit complex transitions between solid-like and fluid-like states. Although natural granular particles typically have irregular shapes, the impact of particle angularity on granular flow remains poorly understood. Here, we demonstrate, through laboratory experiments and numerical simulations, that particle angularity controls vibrated granular flow. Highly angular particles sustain long-lived convective motion, whereas smoother (more rounded) particles rapidly form dense, solid-like structures that suppress fluidization. We further show that rolling resistance models commonly used in simulations fail to fully capture these angularity-driven effects. Our findings challenge standard simulation approaches and indicate that natural granular flows (e.g., landslides and planetary regolith) could be far more dynamic than predicted by spherical-particle approximations. This underscores the crucial but often underappreciated role of particle shape in granular physics.