上游建筑对街道峡谷内流场和污染物分布特征的影响

发布时间：2018-03-08 06:45

本文选题：上游建筑　切入点：行列式街谷　出处：《东华大学》2015年硕士论文　论文类型：学位论文

【摘要】：城市街区空气环境不仅直接影响到街区内居住者及行人的健康，还对整个城市的大气环境有重要影响。随着我国城市机动车保有量的迅速增加，城市街谷内车辆排放的污染物成了影响城市环境的主要原因之一。由于建筑布局对街谷内污染物的扩散产生直接的作用，因此，研究街谷外建筑物对街谷内流场和污染物分布特征对于预测城市空气环境的变化和城市规划都具有重要意义。本文在已有研究的基础上，利用计算流体力学对不同建筑布局的街道峡谷进行了数值模拟研究。在相同背景风速下，分别对不同的上游建筑布局条件下行列式街谷和错列式街谷内的流场和污染物浓度场进行了数值模拟，讨论分析了街谷内不同位置、不同方向、不同高度的气流速度场以及污染物运动和扩散的规律。在这一基础上，，对不同的背景风速下行列式街谷和错列式街谷内部的流场和污染物浓度场进行了数值模拟，讨论了街谷内的气流速度场以及污染物分布特征。模拟结果表明，街谷外阻挡建筑的存在改变了街谷内的二次流，从而对流场和浓度场均有明显影响。在行列式街谷中，无论上游建筑以何种布局存在，都会减小街谷内污染物浓度。若不考虑上游建筑的存在，将会过高估计行列式街谷内污染程度；在错列式街谷中，与街谷建筑并列的上游阻挡建筑会减小街谷内污染物浓度，而与街谷建筑错列布置的阻挡建筑会增大街谷内污染物浓度；数值模拟结果还表明，街谷内污染物的扩散和清除效果受气流速度和涡流特性的共同作用；此外当背景风速增加时，行列式街谷内的气流速度场和污染物浓度分布形态基本不变，变化的只是相应的速度和污染物浓度的大小，而错列式街谷内部的气流速度场分布形态不变，大小改变，浓度场的形态和大小都发生改变。
[Abstract]:The air environment of urban blocks not only directly affects the health of residents and pedestrians, but also has an important impact on the atmospheric environment of the whole city. The pollutants emitted by vehicles in urban streets have become one of the main factors affecting the urban environment. Since the layout of buildings has a direct effect on the diffusion of pollutants in the streets, It is of great significance to study the flow field and pollutant distribution characteristics of buildings outside the street valley in order to predict the change of urban air environment and urban planning. In this paper, based on the existing research, the numerical simulation of street canyons with different building layout is carried out by means of computational fluid dynamics (CFD). The flow field and pollutant concentration field in the determinant street valley and the staggered street valley under different upstream building layout conditions are numerically simulated, and the different positions and directions in the street valley are discussed and analyzed. On the basis of this, the flow field and pollutant concentration field in determinant street valley and staggered street valley under different background wind speeds are numerically simulated. The airflow velocity field and pollutant distribution in the street valley are discussed. The simulation results show that the existence of block building outside the street valley changes the secondary flow in the street valley, thus the flow field and concentration field have obvious influence. If the existence of upstream buildings is not taken into account, the level of pollution in the determinant street valley will be overestimated; in staggered street valley, the concentration of pollutants in the small street valley will be reduced by the upstream barrier building parallel to the street valley building, The results of numerical simulation also show that the diffusion and removal effect of pollutants in street valley is affected by the characteristics of air velocity and eddy current. In addition, when the background wind speed increases, the flow velocity field and pollutant concentration distribution in the determinant street valley are basically unchanged, but only the corresponding velocity and pollutant concentration are changed. However, the distribution of airflow velocity field in staggered street valley is invariant, the size is changed, and the shape and size of concentration field are changed.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X51

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