Study On Simulation Of Pedestrian Evacuation In Chamber Based On Cellular Automaton

With the sustainable development of society and economy, and the acceleration of urbanization process, urban population explosive growth, cinemas, theatres, shopping malls, convention centers, and other crowded public places constantly emerge. At the same time, urban disasters and major emergencies are more serious threats. In recent years, earthquake, fire, stampede and other accidents occur frequently, causing heavy casualties. It is an exigent problem that how to conduct scientific and effective evacuation when emergency incident happen have became the hotspot and keystone of study on public safety and fire safety field. Therefore, research on the characteristic of individual microcosmic behavior and holistic macro behavior, and the mechanism of evacuation phenomena in the occupant evacuation process has significant practical value.The issue of occupant evacuation is a very complicated nonlinear physical problem. The study on the mechanism of pedestrian characteristic, evacuation phenomena and other correlative questions have formed the theories of the pedestrian flow dynamics, also established various emulated models about pedestrian flow. Among these models, cellular automaton model has been widely used in simulation and investigation of pedestrian flow and occupant evacuation. Because cellular automaton is a discrete mathematical model in space, time and state, we can simulate the nonlinear physical phenomenon by leaving out solving the differential equation and establishing rules directly. The model has a strong ability to simulate diverse physical systems and nature phenomenon.In this paper, considering the practical behavior characteristics of pedestrian and the building structure characteristics of the typical public places, we adjust the pedestrian moving rules rationally and propose a new cellular automaton evacuation model based on the existed cellular automata model. We simulate and study the occupant evacuation process in different scenes by computer, and analyze the effect on evacuation time, also investigate the mechanism of evacuation dynamics.The main texts are the followings: 1. Considered desk and chair affecting pedestrian moving velocity, we propose a new cellular automaton evacuation model with two seating and desk regions, and analyze the effect of the occupant density, different exit positions and internal layout on evacuation time. The numerical results demonstrate that:With the greater occupant density, the effect of the seating region on pedestrian evacuation will be much more evident, and the evacuation time increase; When the exit is designed on the side, it should not face to the desks and seats; aisles closed to the two side of the wall are necessary, especially that it is very beneficial for the aisles closed to the exit side of the wall. In order to achieve optimal evacuation efficiency, considered the effect of the number and width of aisle on evacuation time, the internal layout should be made so that the pedestrian can leave the seating region much more quickly, and the exit should not be formed dense congestion.2. Because of poor light or emergency event such as power failure and fire occurs in large cinemas, pedestrian sight is affected. So that the evacuation process in this case is different from the normal one, and show different evacuation dynamics characteristics. In order to investigate the evacuation process with affected pedestrian sight, an improved cellular automata evacuation model is proposed on the basis of the previous cellular automata model. In the model, the space to be evacuated is divided into exit visible area and blind area by pedestrian sight radius. Pedestrian have varied movement in different evacuation areas, including movement to the exit, movement in fixed direction, movement along the wall, changing movement direction and so on. We study the evacuation process in cinemas via the model and discuss the effect of exit visible area on evacuation process. The numerical results demonstrate that:the radius of exit visible area is the key factor in evacuation; pedestrian in blind area select the movement direction to move blindly and randomly, delaying collectivity evacuation time. Finally, we simulate the evacuation process with evacuation indication sign installed in aisles of the blind area, and contrasted it with the previous evacuation. The results show that it is very beneficial to aisles with evacuation indication sign for the evacuation process.3. In order to describe the pedestrian dynamics more carefully in occupant evacuation process, considered the case that pedestrian have multi-direction of movement and manifold movement velocity, we divide the occupied space of a pedestrian into many small grids and propose a new multi-grid model based on the idea of multi-grid model. We simulate the occupant evacuation process in room and get the different evacuation dynamics which traditional single-grid model can not depict:①The motion distance of a pedestrian in single time step do not match with the size of a pedestrian;②the pedestrians in the exit are out of alignment;③a single pedestrian takes up the exist, it is better to describe the effect of exit restrictions on the flow. We analyze that the effect of number of occupant, width of exit on evacuation time, and compare with the case of single-grid model. The numerical results have some guide significance to occupant evacuation in urgent instancesFinally, we give the conclusions of our works and present the prospect of further research of pedestrian flow.