Abstract
We study the passage of active and passive granular particles through a bottleneck under gravitational bias. The grains are pharmaceutical capsules with spherocylindrical shapes on a vibrating table. The vibrating ground plate is slightly tilted in order to break the in-plane symmetry and to give particles a motivation to move in a preferential direction. The passage through a narrow gate with openings comparable to the grain length is studied using video imaging. Particle positions and velocities are extracted from the recorded frames. We find striking differences between the behaviour of asymmetric, active capsules and symmetric, passive ones. The active grains show an astonishingly strong dependence of the passage rates on the gate width, while for passive grains, this dependence is linear as expected. The cumulative distributions of delays between subsequent particles passing the outlet, a key parameter in egress studies, also differ substantially between active and passive grains. Tilt angle and excitation parameters have only little influence on the observed dynamic features, they merely rescale time.
Highlights
The evacuation of a crowd of people from a room, egress of animals from a corral and discharge of granular material from a silo are, for different reasons, very active, interrelated topics of current research
A more general review of the dynamics of systems of active particles was provided by Bechinger et al [21]
In order to restrict the data in this paper to the essentials, we present as examples an excitation strength dependence at fixed tilt and orifice (Fig. 11), an orifice size dependence with fixed tilt and excitation (Fig. 12), and a tilt angle dependence at fixed orifice and excitation parameters (Fig. 13)
Summary
The evacuation of a crowd of people from a room, egress of animals from a corral and discharge of granular material from a silo are, for different reasons, very active, interrelated topics of current research. In crowds of humans or animals, an even more severe consequence is a build-up of high pressure near the outlet [28,29,30,31], which may lead to casualties and unresolvable blockages of the door In both biological and granular systems, the prevention of clogs, and a minimization of the total time needed for emptying the room or container (the egress time) and the avoidance of strong pressure fluctuations are of substantial importance. The motivation to pass an outlet is set by a certain stimulus of the individuals, studies of granular material discharging from hoppers and silos typically rely exclusively on gravity forcing the grains toward the exit. We discuss our results in the context of typical exit scenarios from the literature
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
