Mechanically driven particles as simple models for silo discharge, collective behavior of animate beings, and human egress dynamics

The collective behavior of large ensembles of interacting dynamic objects is an ubiquitous phenomenon that is still not fully understood even today. For example, passages through bottlenecks are often crucial situations that may delay or inhibit the motion of particles, animals, humans, or vehicles. It is often difficult to obtain experimental data under systematic parameter variations, particularly when biological objects are involved. We introduce here purely mechanical experiments with symmetrically and asymmetrically shaped particles that are excited by a vibrating horizontal ground plate. Active and passive dynamics can be mimicked by proper adjustment of the weight distributions in the particles, and the level of activity can be controlled by excitation parameters. A slight tilt of the ground plate can simulate drag in a preferential direction. All these parameters can be conveniently varied in this kitchen-table experiment and optical particle tracking yields all relevant information for a statistical analysis.