Pressure dynamics in the bottleneck flow of self-propelled particles

Abstract

We present an experimental investigation of the pressure dynamics during the flow of self-propelledparticles through narrow passages. When the ensemble is flowing, pressure fluctuates around aconstant value that does not depend on the crowd size, suggesting that the orifice locally determinesthe dynamics in this scenario. On the contrary, when the system clogs, pressures are higher forlarger crowd sizes, highlighting the importance of the whole collectivity in the process. Then, bycorrelating the pressure evolution with the exit time of the self-propelled particles, we discoverthat when a clog is resolved, pressure suddenly drops as a consequence of system reorganization.After this dramatic event, there is a sustained pressure growth over time that shows a square rootdependence, compatible with the structural aging that has been proposed to be behind the broadtail distributions of clogging times.