Riemann problems with non--local point constraints and capacity drop

In the present note we discuss in details the Riemann problem for a one--dimensional hyperbolic conservation law subject to a point constraint. We investigate how the regularity of the constraint operator impacts the well--posedness of the problem, namely in the case, relevant for numerical applications, of a discretized exit capacity. We devote particular attention to the case in which the constraint is given by a non--local operator depending on the solution itself. We provide several explicit examples. We also give the detailed proof of some results announced in the paper [Andreainov, Donadello, Rosini, "Crowd dynamics and conservation laws with non--local point constraints and capacity drop", which is devoted to existence and stability for a more general class of Cauchy problems subject to Lipschitz continuous non--local point constraints.Comment: 19 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1304.628

An improved version of the Hughes model for pedestrian flow

Roger Hughes proposed a macroscopic model for pedestrian dynamics, in which individuals seek to minimize their travel time but try to avoid regions of high density. One of the basic assumptions is that the overall density of the crowd is known to every agent. In this paper we present a modification of the Hughes model to include local effects, namely limited vision, and a conviction towards decision making. The modified velocity field enables smooth turning and temporary waiting behavior. We discuss the modeling in the micro- and macroscopic setting as well as the efficient numerical simulation of either description. Finally we illustrate the model with various numerical experiments and evaluate the behavior with respect to the evacuation time and the overall performance

Lois de conservation pour la modélisation des mouvements de foule

In this thesis, we consider nonclassical problems brought out by the macroscopic modeling of pedestrian flow. The first model consists of a conservation law with a discontinuous flux, the second is a mixed hyperbolic-elliptic system of conservation laws and the last one is a nonlocal equation. In the first chapter, we use the Hughes model in one space-dimension to represent the evacuation of a corridor with two exits. The model couples a conservation law with discontinuous flux to an eikonal equation. We implement the wave front tracking scheme, treating explicitly the solution nonclassical behavior at the turning point, to provide a reference solution, which is used to numerically test the convergence of classical finite volume schemes. In the second chapter, we model the crossing of two groups of pedestrians walking in opposite directions with a system of conservation laws whose flux depends on the two densities. This system loses its hyperbolicity for certain density values. We assist to the rising of persistent but bounded oscillations, that lead us to the recast of the problem in the framework of measure-valued solutions. Finally we study a nonlocal model of pedestrian flow in two space-dimensions. The model consists of a conservation law whose flux depends on a convolution of the density. With this model, we solve an optimization problem for a room evacuation with a descent method, evaluating the impact of the explicit computation of the cost function gradient with the adjoint state method rather than approximating it with finite differences.Dans cette thèse, on considère plusieurs problèmes issus de la modélisation macroscopique des mouvements de foule. Le premier modèle consiste en une loi de conservation avec un flux discontinu, le second est un système mixte hyperbolique-elliptique et le dernier est une équation non-locale. D'abord, on utilise le modèle de Hughes une dimension pour décrire l'évacuation d'un couloir avec deux sorties. Ce modèle couple une loi de conservation avec un flux discontinu à une équation eikonale. On implémente la méthode de suivi de fronts, qui traite explicitement le comportement de la solution non-classique au point de rebroussement, afin d'obtenir des solutions de référence. Elles serviront à tester numériquement la convergence de schémas aux volumes finis classiques. Ensuite, on modélise le croisement de deux groupes marchant dans des directions opposées avec un système de lois de conservation mixte hyperbolique-elliptique dont le flux dépend des deux densités. Le système perd son hyperbolicité pour certainement valeurs de densité. On assiste à l'apparition d'oscillations persistantes mais bornées, ce qui conduit à la reformulation du problème associé dans le cadre des mesures de probabilités. Finalement, on étudie un modèle non-local de trafic piétonnier en deux dimensions. Le modèle consiste en une loi de conservation dont le flux dépend d'une convolution de la densité. Avec ce modèle, on résout un problème d'optimisation pour une évacuation d'une salle avec une méthode de descente, évaluant l'impact du calcul explicite du gradient de la fonction coût avec la méthode de l'état adjoint plutôt que son approximation par différences finies