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Hydrodynamics of polarized crowds : experiments and theory

Abstract : Modelling crowd motion is central to situations as diverse as risk prevention in mass events and visual effects rendering in the motion picture industry. The difficulty to perform quantitative measurements in model experiments, and the lack of reference experimental system, have however strongly limited our ability to model and control pedestrian flows. The aim of this thesis is to strengthen our understanding of human crowds, following two distinct approaches.First, we designed a numerical model to study the lane formation process among bidirectional flows of motile particles. We first evidenced the existence of two distinct phases: one fully laned and one homogeneously mixed, separated by a critical phase transition, unique to active systems. We then showed with a hydrodynamic approach that the mixed phase is algebraically correlated in the direction of the flow. We elucidated the origin of these strong correlations and proved that they were a universal feature of any system of oppositely moving particles, active of passive.Second, we conducted a substantial experimental campaign to establish a model experiment of human crowds. For that purpose we performed systematic measurements on crowds composed of tens of thousands of road-race participants in start corrals, a geometrically simple setup. We established that speed information propagates through polarized crowds over system spanning scales, while orientational information is lost in a few seconds. Building on these observations, we laid out a hydrodynamic theory of polarized crowds and demonstrated its predictive power.
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Submitted on : Tuesday, December 4, 2018 - 12:53:09 PM
Last modification on : Thursday, November 21, 2019 - 1:43:27 AM


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  • HAL Id : tel-01943999, version 1


Nicolas Bain. Hydrodynamics of polarized crowds : experiments and theory. Soft Condensed Matter [cond-mat.soft]. Université de Lyon, 2018. English. ⟨NNT : 2018LYSEN078⟩. ⟨tel-01943999⟩



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