【作者】 朱强；

【导师】 亢燕铭；

【作者基本信息】 东华大学 ， 供热、供燃气、通风及空调工程， 2015， 硕士

【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。更多还原

【Abstract】 Local air environment in building clusters not only has directly effects on the health of theresidents who live in the district and pedestrians, but also has significant impacts on urban airenvironment. With the rapid increase of the city’s vehicle fleet, the pollutant emission fromvehicles has become one of the main factors affecting the urban air environment. Because of thebuilding layouts in urban areas have direct effects on the atmospheric dispersion of pollutants, it isimportant to study the airflow fields and pollutant distributions in street canyons for predictingchanges in urban air environment and providing some available information for urban planning.Based on the previous studies, numerical simulations have been conducted for exploring theenvironment of street canyons with different building layouts by employing CFD techniques.Under the same background wind speed, and according to the numerical simulations, the airflowvelocity and the diffusion of pollutants were analyzed for different positions, different directions,and different height. Moreover, same analyses and discussions were made under differentbackground wind speeds.The numerical results showed that the upstream buildings change the local wind speed anddistort the secondary flows in the canyons and thus have significant effects on the flow andconcentration fields. In the regular street canyons, the average pollutant concentrations could bereduced regardless of layout of the upstream buildings. The average concentration would beoverestimated by numerical simulations without considering the existence of the upstreambuildings in practice. Inside the staggered street canyons, when upstream buildings are alignedwith street canyons, the pollutant concentrations in the street canyon could be reduced by theblocking effect. In contrast, when the upstream buildings are staggered with the canyons, theconcentrations could be increased. The results also showed that the pollutant dispersion andremoval in street canyons are effected by both the airflow velocity and local vortex characteristics.In addition, for regular street canyon, when the background wind speed increases, the features ofthe airflow velocity and pollutant concentration distribution will not be changed, only the values of the speed and concentration can be changed. For the staggered canyon, both the airflow patternand the concentration field will be changed.更多还原