Ferrer, L.M. (Luis Miguel)
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- Experimental proof of faster-is-slower in systems of frictional particles flowing through constrictions(2015) Pugnaloni, L.A. (Luis A.); Parisi, D.R. (D. R.); Zuriguel-Ballaz, I. (Iker); Peralta, J.P. (Juan Pablo); Martín-Gómez, C. (César); Pastor-Gutierrez, J.M. (José Martín); Ferrer, L.M. (Luis Miguel); Maza-Ozcoidi, D. (Diego); Montero, Á. (Ángel); Gago, P.A. (Paula A.)The “faster-is-slower” (FIS) effect was first predicted by computer simulations of the egress of pedestrians through a narrow exit [D. Helbing, I. J. Farkas, and T. Vicsek, Nature (London) 407, 487 (2000)]. FIS refers to the finding that, under certain conditions, an excess of the individuals’ vigor in the attempt to exit causes a decrease in the flow rate. In general, this effect is identified by the appearance of a minimum when plotting the total evacuation time of a crowd as a function of the pedestrian desired velocity. Here, we experimentally show that the FIS effect indeed occurs in three different systems of discrete particles flowing through a constriction: (a) humans evacuating a room, (b) a herd of sheep entering a barn, and (c) grains flowing out a 2D hopper over a vibrated incline. This finding suggests that FIS is a universal phenomenon for active matter passing through a narrowing.
- Clogging transition of many-particle systems flowing through bottlenecks(2014) Clement, E. (E.); Pugnaloni, L.A. (Luis A.); Parisi, D.R. (D. R.); Pagonabarraga, I. (Ignacio); Zuriguel-Ballaz, I. (Iker); Peralta, J.P. (Juan Pablo); Cruz-Hidalgo, R. (Raúl); Ferrer, L.M. (Luis Miguel); Lozano, C. (Celia); Maza-Ozcoidi, D. (Diego); Janda, A. (Álvaro); Montero, Á. (Ángel); Gago, P.A. (Paula A.)
- Flow and clogging of a sheep herd passing through a bottleneck(2015) Zuriguel-Ballaz, I. (Iker); Martín-Gómez, C. (César); Pastor-Gutierrez, J.M. (José Martín); Ferrer, L.M. (Luis Miguel); Montero, Á. (Ángel); Ramos, J.J. (J.J.)We present an experimental study of a flock passing through a narrow door. Video monitoring of daily routines in a farm has enabled us to collect a sizable amount of data. By measuring the time lapse between the passage of consecutive animals, some features of the flow regime can be assessed. A quantitative definition of clogging is demonstrated based on the passage time statistics. These display broad tails, which can be fitted by power laws with a relatively large exponent. On the other hand, the distribution of burst sizes robustly evidences exponential behavior. Finally, borrowing concepts from granular physics and statistical mechanics, we evaluate the effect of increasing the door size and the performance of an obstacle placed in front of it. The success of these techniques opens new possibilities regarding their eventual extension to the management of human crowds.
- Effect of obstacle position in the flow of sheep through a narrow door(2016) Zuriguel-Ballaz, I. (Iker); Martín-Gómez, C. (César); Pastor-Gutierrez, J.M. (José Martín); Olivares, J. (Jorge); Ferrer, L.M. (Luis Miguel); Montero, Á. (Ángel); Ramos, J.J. (J.J.)In a recent work Phys. Rev. E 91, 022808 (2015)PLEEE81539-375510.1103/PhysRevE.91.022808] it was reported that placing an obstacle in front of a gate has a beneficial effect in the flow of sheep through it. Here, we extend such results by implementing three different obstacle positions. We have observed that the flow is improved in two cases, while it worsens in the other one; the last instance happens when the obstacle is too close to the door. In this situation, the outcomes suggest that clogging develops between the doorjamb and the obstacle, contrary to the cases when the obstacle is farther, in which case clogging always occurs at the very door. The effectiveness of the obstacle (a strategy put forward to alleviate clogging in emergency exits) is therefore quite sensitive to its location. In addition, the study of the temporal evolution of the flow rate as the test develops makes evident a steady behavior during the entire duration of the entrance. This result is at odds with recent findings in human evacuation tests where the flow rate varies over time, therefore challenging the fairness of straightforward comparisons between pedestrian behavior and animal experimental observations.