不同来流风向下Y型城市道路交叉口污染物扩散规律的研究

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3.0 侯斌 2025-01-09 10 4 5.54MB 87 页 15积分

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摘要

城市道路交叉口是城市交通的关键组成部分，城市道路交叉口的车流量大、

密度集中，各种机动车辆的运动也很复杂，造成机动车尾气排放率增大。同时，

城市交叉口周围的高层建筑阻碍了污染物在大气中的扩散，而大量行人聚集在交

叉口停车线前，长时间暴露于污染物中，严重影响了身体健康，因此深入研究交

叉口处的污染物对流扩散规律具有重要的现实意义。机动车尾气在城市道路交叉

口的扩散情况主要由周围的流场所决定，而该流场受到来流风向的影响极大。国

内外对于城市交叉口处的污染物对流扩散规律的关注越来越多，但是主要考虑的

都是不同街道布局和形态对污染物扩散的影响，还没有广泛应用 CFD 方法对来流

风向的变换进行研究。本文采用 CFD 数值模拟的方法，研究不同来流风向条件下

Y型城市道路交叉口内的空气通量、气流运动、旋涡结构特征和污染物扩散分布

的情况，分析不同来流风向对交叉口内气流运动和污染物扩散的影响。同时针对

四种不同布局的城市道路交叉口处的污染物对流扩散进行了风洞实验，对数值模

拟的结果进行了验证分析。

采用三维不可压缩流动的时均化 N-S 方程、标准 k-ε湍流模型和污染物对流扩

散方程，建立起 Y型城市道路交叉口内气流运动和污染物扩散的三维数值仿真模

型。在 ANSYS FLUENT 14.5 平台上对所建立的模型进行数值求解。

本文通过对八种不同来流风向下的 Y型交叉口内气流运动与污染物扩散进行

了三维数值模拟。结果表明交叉口内气流运动、旋涡结构、空气交换量和污染物

分布与自由来流风向密切相关：

(1) 交叉口中心垂直方向的空气交换程度与来流风向有直接关系。在 0°到135°

和-0°（即 180°）到-135°两个风向区域内，来流风向与截面 S4 的空气通量分别成

抛物线形式。而 0°和180°时空气通量的绝对值最小，此工况下污染物最不易于扩

散。来流风向绝对值相等时，其各个截面上的通量大小基本相等。不同工况下该

街道内相同位置处的空气通量减少和增加的幅度差不多，即图形大致关于θ的某

个值对称。

(2) 随着来流风向的变换，各街道内的气流流场均变化很大。与来流风向不平

行的街道入口往往更容易形成漩涡，同时由于漩涡的影响，入口处迎风面的流场

强度往往大于背风面。而与来流风向平行的街道出口处更容易形成双漩涡。交叉

口内流场密集风速很大，而在建筑物的后侧，流场强度往往很小。

(3) 不同来流风向会影响 Y型城市道路交叉口的污染物扩散，近地面的污染物

扩散在 θ=0°的工况中，污染物浓度很高，污染物没有扩散到街道外。在θ=90°的

工况中，来流风向与污染源平行，污染物扩散能力最强，浓度最低。且街道一和

街道三内的污染普遍比街道二严重。

(4) 不同街道的同一样本点在不同来流风向下的无量纲浓度随高度变化曲线

各不相同，但是总体趋势通常都是随着垂直高度的增加逐渐降低。但是由于街道

二内污染不严重，因此街道二的两个样本点在工况 2、5、6、7、8的无量纲浓度

值始终接近于零，几乎不随高度发生改变。

本次风洞实验使用线源污染物发放装置，集成一套污染物瞬态浓度场激光片

光监测系统。做好实验前期工作后，对 Y型交叉口内的污染物扩散分布进行风洞

实验研究，得到相应工况的污染物分布图。通过对交叉口内污染物分布的数值模

拟结果和风洞实验结果进行对比分析，得出数值模拟结果与风洞实验结果定性一

致。同时证明了采用标准 k-ε湍流模型模拟交叉口内气流运动和污染物扩散的可靠

性。

本研究的成果对于城市道路交叉口建筑布局、交叉口道路设置、城市交通规

划以及环境监测中科学合理布设测试点位置具有指导意义。

关键词：不同来流风向 Y型交叉口风洞实验数值模拟

ABSTRACT

The urban street intersection is the key component of the urban traffic. Large urban

intersection traffic, concentration, all complicated kinds of motor vehicle movement

cause motor vehicle exhaust emissions increased. At the same time, the high-rise

buildings around the urban intersection hinder the diffusion of pollutants in the

atmosphere, and gathered a large number of pedestrians in the intersection exposure to

pollutants for a long time, seriously affected their health, thus further study of

intersection convection diffusion of pollutants has important practical significance.

Motor vehicle exhaust diffusion of the main streets in the city intersection is determined

by the flow around, and the flow field is affected by the wind flow. More and more

attention has been drawn at home and abroad of pollutants convection diffusion

regularity of urban intersection, but the main consideration is the influence of different

street layout and form of pollutant diffusion. The method of CFD to change wind flow

has not been widely used. This article adopts the method of CFD numerical simulation,

studying the Y type under the conditions of different wind flow inside the urban

intersection to analyze the influence of different wind flow to air flow movement and

pollutant diffusion.

Using the three dimensional incompressible flow homogenization navier-stokes

equation, the standard k - epsilon turbulence model and the pollutants convection

diffusion equation, build Y type air flow movement and three-dimensional numerical

simulation of contaminant distribution in the model.In ANSYS FLUENT 14.5 platform

to conducted the established numerical model.

This paper includes eight different directions of airflow in the intersection. The

results show that airflow in intersection movement, vortex structures, air exchange

capacity and pollutant distribution is closely related to the direction of the wind:

(1) Air exchange in vertical direction is directly related to wind direction. In 0° to

135° and -0° (180°)to 135° two wind area, wind flow and section S4 air flux is into a

parabola form. When the direction are 0° and 180°, the absolute value of the air flux is

minimum, the pollutants under which condition is not easy to spread. When the absolute

value of wind flow is equal, the flux on each cross section is basic equal. Under

different working conditions of the streets in the same location , if their air flux decrease

and increase ,the graphic is roughly symmetrical about a value of X.

(2) As the wind flow to transform, the air flow field were changed a lot.And wind

flow to the unparallel street entrance is often easier to form vortex, at the same time

because of the influence of vortex at the entrance, the windward surface flow field

intensity is often greater than the leeward side. And parallel to the wind flow the street

is more likely to form double vortex at the exit. The wind speed in the intersection is

large, and at the back of the building, the flow field is often very small.

(3) Different wind flow affect Y-type urban street intersection pollutant diffusion.

When θ = 0°, high concentrations of contaminants pollutant can not spread to the

outside of the streets. When θ = 90°, because wind flow is parallel to the pollution

source, pollutant diffusion is most powerful. Street 1 and street 3 is common more

polluted than street 2.

(4) The same sample points of the different streets in different dimensionless

concentration with height curve of wind flow are not identical, but the overall trend is

usually reduced gradually with the increase of vertical height.But because of pollution

in the street not serious, so the street 2 of three sample points in the condition of 2, 5, 6,

7, 8, the nondimensional density is always close to zero, almost not changed with

height.

A line source distribution attached to the large environmental wind tunnel were

designed, and a light-monitoring system in the transient laser sheet for pollutant

concentration was formed. On this basis, the Y-type intersection distribution of pollutant

diffusion in the wind tunnel experiments, the distribution of pollutants at corresponding

operation. Based on the distribution of pollutants in the intersection of the results of

numerical simulation and wind tunnel experimental results, this paper compares and

analyzes the results of numerical simulation and wind tunnel experimental results

qualitatively. At the same time proved that the standard k - epsilon turbulent air flow

movement to simulate intersection is reliable.

This research results show that it has guiding significance for urban road traffic

planning, urban road intersection layout and the environmental monitoring in the

scientific and rational arrangement of the test point position.

Key Word: different wind direction, y-type intersection, CFD, wind

tunnel experiment

中文摘要

ABSTRACT

第一章绪论 ......................................................... 1

1.1 研究背景 ....................................................... 1

1.1.1 空气污染现状 ............................................... 1

1.1.2 城市道路交叉口污染现状 ..................................... 4

1.1.3 污染物扩散的影响因素 ....................................... 4

1.2 交叉口气流运动与污染物扩散研究方法 ............................. 6

1.3 论文的目的、意义及主要内容 ................................... 9

1.4 研究创新点 .................................................. 10

第二章 Y 型城市道路交叉口内气流运动与污染扩散的数值仿真模型构建 ..... 11

2.1 城市道路交叉口简介 ............................................ 11

2.2 CFD 模型 ...................................................... 12

2.2.1 气流运动控制方程 .......................................... 13

2.2.2 污染物对流扩散方程 ........................................ 18

2.2.3 网格技术 .................................................. 19

2.2.4 数值算法 .................................................. 21

2.3 本章小结 ...................................................... 21

第三章不同来流风向下的 Y型交叉口处的气流运动及污染物扩散的数值模拟 22

3.1 Y 型交叉口的物理模型 .......................................... 22

3.2 数学模型 ...................................................... 23

3.2.1 控制方程 .................................................. 23

3.2.2 网格划分 .................................................. 25

3.2.3 边界条件 .................................................. 26

3.2.4 数值计算 .................................................. 28

3.3 空气通量及交叉口流场分析 ...................................... 29

3.3.1 交叉口垂直通量分析 ........................................ 30

3.3.2 三个街道各截面空气通量分析 ................................ 31

3.3.3 交叉口处流场分析 .......................................... 34

3.4 污染物扩散分析 ............................................... 40

3.4.1 近地面污染物浓度分析 ..................................... 40

3.4.2 无量纲浓度 K的分析 ....................................... 45

3.5 本章小结 ...................................................... 50

第四章 Y 型城市道路交叉口内污染物对流扩散的风洞实验 ................. 52

4.1 风洞简介 ...................................................... 52

4.2 上海理工大学环境风洞概况 ...................................... 53

4.3 Y 型城市道路交叉口风洞实验 .................................... 57

4.3.1 实验目的及意义 ............................................ 57

4.3.2 实验仪器、设备和实验模型 .................................. 57

4.3.3 测量方法 .................................................. 60

4.3.4 实验步骤 .................................................. 61

4.3.5 实验结果 .................................................. 62

4.4 本章小结 ...................................................... 64

第五章数值模拟与风洞实验对比分析 .................................. 65

5.1 Y 型交叉口内污染分布数值模拟与风洞实验对比 .................... 65

5.2 本章小结 ...................................................... 67

第六章结论与展望 .................................................. 68

6.1 结论 .......................................................... 68

6.2 展望 .......................................................... 69

附录 .............................................................. 70

参考文献 ........................................................... 72

在读期间公开发表的论文和承担科研项目及取得成果 ..................... 82

致谢 .............................................................. 83

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