749 research outputs found
Thermocapillary flows and interface deformations produced by localized laser heating in confined environment
The deformation of a fluid-fluid interface due to the thermocapillary stress
induced by a continuous Gaussian laser wave is investigated analytically. We
show that the direction of deformation of the liquid interface strongly depends
on the viscosities and the thicknesses of the involved liquid layers. We first
investigate the case of an interface separating two different liquid layers
while a second part is dedicated to a thin film squeezed by two external layers
of same liquid. These results are predictive for applications fields where
localized thermocapillary stresses are used to produce flows or to deform
interfaces in presence of confinement, such as optofluidics
Quantitative Description of Pedestrian Dynamics with a Force based Model
This paper introduces a space-continuous force-based model for simulating
pedestrian dynamics. The main interest of this work is the quantitative
description of pedestrian movement through a bottleneck. Measurements of flow
and density will be presented and compared with empirical data. The results of
the proposed model show a good agreement with empirical data. Furthermore, we
emphasize the importance of volume exclusion in force-based models.Comment: 4 pages, 7 figures, 2009 IEEE/WIC/ACM International Joint Conferences
on Web Intelligence and Intelligent Agent Technologies (WI-IAT 2009), 15-18
September 2009, in Milano, Italy, 200
Influence of the number of predecessors in interaction within acceleration-based flow models
In this paper, the stability of the uniform solutions is analysed for
microscopic flow models in interaction with predecessors. We calculate
general conditions for the linear stability on the ring geometry and explore
the results with particular pedestrian and car-following models based on
relaxation processes. The uniform solutions are stable if the relaxation times
are sufficiently small. The analysis is focused on the relevance of the number
of predecessors in the dynamics. Unexpected non-monotonic relations between
and the stability are presented.Comment: 18 pages, 14 figure
Quantitative Verification of a Force-based Model for Pedestrian Dynamics
This paper introduces a spatially continuous force-based model for simulating
pedestrian dynamics. The main intention of this work is the quantitative
description of pedestrian movement through bottlenecks and in corridors.
Measurements of flow and density at bottlenecks will be presented and compared
with empirical data. Furthermore the fundamental diagram for the movement in a
corridor is reproduced. The results of the proposed model show a good agreement
with empirical data.Comment: 8 pages, 7 figures, Proceedings of Traffic and Granular Flow (TGF)
200
Validated force-based modeling of pedestrian dynamics
This dissertation investigates force-based modeling of pedestrian dynamics. Having the quantitative validation of mathematical models in focus principle questions will be addressed throughout this work: Is it manageable to describe pedestrian dynamics solely with the equations of motion derived from the Newtonian dynamics?
On the road to giving answers to this question we investigate the consequences and side-effects of completing a force-based model with additional rules and imposing restrictions on the state variables. Another important issue is the representation of modeled pedestrians. Does the geometrical shape of a two dimensional projection
of the human body matter when modeling pedestrian movement? If yes which form is most suitable? This point is investigated in the second part while introducing a new force-based model. Moreover, we highlight a frequently underestimated aspect in force-based modeling which is to what extent the steering of pedestrians influences their dynamics? In the third part we introduce four possible strategies to define the desired direction of each pedestrian when moving in a facility. Finally, the effects of the aforementioned approaches are discussed by means of
numerical tests in different geometries with one set of model parameters. Furthermore, the validation of the developed model is questioned by comparing simulation results with empirical data
Optohydrodynamics of soft fluid interfaces : Optical and viscous nonlinear effects
Recent experimental developments showed that the use of the radiation
pressure, induced by a continuous laser wave, to control fluid-fluid interface
deformations at the microscale, represents a very promising alternative to
electric or magnetic actuation. In this article, we solve numerically the
dynamics and steady state of the fluid interface under the effects of buoyancy,
capillarity, optical radiation pressure and viscous stress. A precise
quantitative validation is shown by comparison with experimental data. New
results due to the nonlinear dependence of the optical pressure on the angle of
incidence are presented, showing different morphologies of the deformed
interface going from needle-like to finger-like shapes, depending on the
refractive index contrast. In the transient regime, we show that the viscosity
ratio influences the time taken for the deformation to reach steady state
Investigation of Voronoi diagram based Direction Choices Using Uni- and Bi-directional Trajectory Data
In a crowd, individuals make different motion choices such as "moving to
destination", "following another pedestrian", and "making a detour". For the
sake of convenience, the three direction choices are respectively called
destination direction, following direction and detour direction in this paper.
Here, it is found that the featured direction choices could be inspired by the
shape characteristics of Voronoi diagram. To be specific, in the Voronoi cell
of a pedestrian, the direction to a Voronoi node is regarded as a potential
"detour" direction, and the direction perpendicular to a Voronoi link is
regarded as a potential "following" direction. A pedestrian generally owns
several alternative Voronoi nodes and Voronoi links in a Voronoi cell, and the
optimal detour and following direction are determined by considering related
factors such as deviation. Plus the destination direction which is directly
pointing to the destination, the three basic direction choices are defined in a
Voronoi cell. In order to evaluate the Voronoi diagram based basic directions,
the empirical trajectory data in both uni- and bi-directional flow experiments
are extracted. A time series method considering the step frequency is used to
reduce the original trajectories' swaying phenomena which might disturb the
recognition of actual forward direction. The deviations between the empirical
velocity direction and the basic directions are investigated, and each velocity
direction is classified into a basic direction or regarded as an inexplicable
direction according to the deviations. The analysis results show that each
basic direction could be a potential direction choice for a pedestrian. The
combination of the three basic directions could cover most empirical velocity
direction choices in both uni- and bi-directional flow experiments.Comment: 10pages, 12 figure
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