Pressure dynamics in the bottleneck flow of self-propelled particles

TL;DR

This study investigates pressure fluctuations in self-propelled particles flowing through narrow passages, revealing local dynamics during flow and collective effects during clogging, with implications for understanding clogging and system reorganization.

Contribution

It provides experimental insights into pressure behavior and clogging dynamics in self-propelled particle flow, highlighting local versus collective effects and pressure evolution after clog resolution.

Findings

Pressure remains constant during flow, independent of crowd size.

Higher pressures are observed during clogging for larger crowds.

Pressure drops suddenly when a clog is resolved, followed by a square root growth indicating aging.

Abstract

We present an experimental investigation of the pressure dynamics during the flow of self-propelled particles through narrow passages. When the ensemble is flowing, pressure fluctuates around a constant value that does not depend on the crowd size, suggesting that the orifice locally determines the dynamics in this scenario. On the contrary, when the system clogs, pressures are higher for larger crowd sizes, highlighting the importance of the whole collectivity in the process. Then, by correlating the pressure evolution with the exit time of the self-propelled particles, we discover that 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 root dependence, compatible with the structural aging that has been proposed to be behind the broad tail distributions of clogging times.