基于CFD和PIV技术的街道峡谷内污染物扩散规律研究

发布时间：2018-05-04 16:00

本文选题：街道峡谷 + 污染物扩散　；参考：《山东建筑大学》2015年硕士论文

【摘要】：随着我国工业化和城市化进程的加快,近年来城市机动车数量迅速增长,机动车排放的污染物已成为城市大气污染的主要来源。城市化过程中为节约土地资源,城市建设主要选择高层建筑,高层建筑的增多形成很多街道峡谷,其对城市环境的影响也越来越大,致使机动车排放的大量有害气体难以扩散出去,积聚在街道峡谷内,使居民日常出行暴露在高浓度机动车尾气污染物中,同时对临街建筑室内空气质量将产生严重影响,严重危及城市居民的身心健康。因此对城市街道机动车排放污染物扩散规律以及对建筑室内外空气质量的影响进行全面研究具有非常重要的现实意义。本文结合大气环境、交通规划、流体力学、数值分析以及城市规划、建筑设计等学科知识,使用数值模拟和风洞实验相结合的方法研究了城市街道峡谷机动车排放污染物的扩散规律和分布情况,为城市街道的合理布局与城市街道的规划建设提供科学的依据,对改善城市居民生活质量,实现城市和交通的可持续发展具有重要意义。本文的研究对象为三条平行的街道峡谷,实际中对应的是济南市三条平行的道路,解放东路、和平路和文化东路。研究工况为来流垂直于街道峡谷长度方向时,四个不同风速下的街道峡谷内气体流速分布特征和污染物浓度分布特征,以及五个不同风向下,孤立型街道峡谷内气体流场特征,还模拟了污染源强的变化和两侧建筑物高度不同对气体扩散的影响,根据流场特征总结出街道峡谷内污染物扩散规律。本文采用数值模拟计算,风洞实验进一步验证的方法,比较客观地总结出街道峡谷内污染物扩散的情况和浓度场分布的特点。全面分析了街道峡谷内污染物扩散的影响因素,包括污染源强度及其与建筑物的距离、风速、风向、风速和风向协同作用、街道峡谷的类型、太阳辐射、人行走廊等因素。建立了城市街道峡谷内污染物传输扩散的数学模型,包括控制流体流动的连续性方程、动量方程、K-ξ双方程以及污染物扩散方程。对街道峡谷内气体流场和污染物浓度分布先进行数值模拟计算,将数值与风洞实验测量的结果进行校对,从而验证了数值模拟的准确性。通过对街道峡谷内污染物传输扩散规律的数值模拟结果的分析,揭示了当来流垂直于街道长度方向时,无论街道中有无障碍物,都会在街道峡谷中形成一个顺时针的旋涡,这个旋涡将污染物带至背风侧,这样一来,背风侧污染物浓度就会高于迎风侧。越靠近下风向,街道峡谷背风侧污染物浓度越高,迎风侧污染物浓度也较上风向的两个街道峡谷迎风侧高。随着风速增大,街道峡谷内部背风侧和迎风侧污染物浓度逐渐减小,但背风侧污染物浓度始终高于迎风侧。同时,也模拟了风向、污染源强、两侧建筑物相对高度对街道峡谷内污染物扩散的影响。搭建了街道峡谷内部流场测量的实验台,将粒子图像测速(PIV)技术应用于风洞实验,对街道峡谷内气体流速分布进行测量,概括了PIV系统中相机光圈数、激光脉冲时间间隔以及示踪粒子的大小对流速分布测量结果的影响。当来流垂直街道长度方向时,对街道峡谷内部的二维流场进行了完整测试,获得了众多实验数据。本文所作的研究为城市区域街道峡谷内机动车排放污染物的控制、交通流量的控制、城市街道的合理布局与城市街道的规划建设,大气污染评价、监测与防治提供理论依据。
[Abstract]:With the accelerated process of industrialization and urbanization in China, the number of urban motor vehicles has increased rapidly in recent years. The pollutants discharged by motor vehicles have become the main source of urban air pollution. In the process of urbanization, the main choice of high rise buildings is to save land resources, and the increase of high-rise buildings has formed a lot of street canyons. The impact of the environment is becoming more and more large, resulting in a large number of harmful gases emitted by motor vehicles, which are difficult to spread out and accumulate in the street canyons. The daily travel of the residents is exposed to the high concentration of vehicle exhaust pollutants. At the same time, the indoor air quality of the street buildings will be seriously affected, which seriously endangers the physical and mental health of the urban residents. Therefore, the city is seriously endangering the physical and mental health of the urban residents. It is of great practical significance to carry out a comprehensive study on the diffusion of pollutants in urban streets and the influence of the indoor and outdoor air quality on buildings. This paper combines the knowledge of atmospheric environment, traffic planning, hydrodynamics, numerical analysis, urban planning, architectural design, and the combination of numerical simulation and wind tunnel experiments. Methods the diffusion law and distribution of vehicle emission pollutants in urban street canyons are studied. It provides a scientific basis for the rational layout of urban streets and the planning and construction of urban streets. It is of great significance to improve the living quality of urban residents and realize the sustainable development of city and traffic. The research object of this paper is three parallel. The street canyon in reality corresponds to the three parallel roads in Ji'nan, the East Road, the peace road and the East Road. The study conditions are the characteristics of gas velocity distribution and the distribution characteristics of the pollutant concentration in the street canyons under four different wind speeds, and the isolated street under five different wind directions. The characteristics of the gas flow in the channel Canyon also simulated the influence of the strong change of the pollution source and the different height of the building on the gas diffusion. According to the characteristics of the flow field, the diffusion law of the pollutant in the street canyon was summed up. The numerical simulation and the square method which was further verified by the wind tunnel experiment were used to objectively summarize the pollutants in the street canyon. A comprehensive analysis of the factors affecting the diffusion of pollutants in the street canyon, including the intensity of the pollution source and its distance from the building, the wind speed, the wind direction, the wind speed and the direction of the wind, the type of street canyons, the solar radiation, the pedestrian corridor and other factors. The pollutant transport in the city street canyon is established. The mathematical model of diffusion, including the continuity equation controlling the flow of the fluid, the momentum equation, the K- zeta double equation and the pollutant diffusion equation, is used to simulate the gas flow field and the concentration distribution of the pollutants in the street canyon, and the results of the numerical and wind tunnel experiments are proofed, thus verifying the accuracy of the numerical simulation. The analysis of the numerical simulation results of the transport and diffusion of pollutants in the street canyon reveals that when the stream is perpendicular to the street length, no matter whether there is an obstacle in the street, a clockwise clockwise vortex is formed in the street canyon, which leads the pollutant to the leeward side, thus the concentration of the contaminant on the leeward side will be high. On the windward side, the closer to the downwind direction, the higher the pollutant concentration in the leeward side of the street canyon, the concentration of the upwind side is higher than the upwind side of the two street canyons. As the wind speed increases, the concentration of the leeward side and the upwind side of the street canyon decreases gradually, but the concentration of the leeward side pollutants is always higher than that in the windward side. The influence of the wind direction, the strong pollution source, the relative height of the buildings on the pollutant diffusion in the street canyon. An experimental platform for the measurement of the flow field in the street canyon is built. The particle image velocimetry (PIV) technology is applied to the wind tunnel experiment. The gas velocity distribution in the street canyon is measured, and the number of the aperture of the camera and the laser pulse in the PIV system is summarized. The influence of the time interval and the size of the tracer particle on the measurement of the velocity distribution. When the stream is perpendicular to the street, the two-dimensional flow field in the street canyon is fully tested and a large number of experimental data have been obtained. This study is for the control of the emission of vehicles in the street canyons in the urban area and the traffic flow. Control, reasonable layout of urban streets, planning and construction of urban streets, air pollution assessment, monitoring and prevention provide theoretical basis.

【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X734.2

【参考文献】