【作者】 张晓伟；

【导师】 朱蒙生；

【作者基本信息】 哈尔滨工业大学 ， 流体力学， 2007， 硕士

【摘要】 随着我国城市化和工业化进程的加快,环境空气污染问题已越来越受到许多研究领域的重视。目前,机动车排放的污染物已被认为是城市环境空气的主要污染来源,而研究表明,汽车尾气的排放主要在0.3～2m之间,正好是人体的呼吸范围,对人体健康损害非常严重,长期暴漏在这种环境中将引发多种疾病。而住宅小区又是人们生活和活动的主要场所,研究污染物在住宅小区内的扩散状况具有现实意义。本文采用计算流体动力学CFD(Computational Fluid Dynamics)的方法,以哈尔滨市某新建住宅小区为研究对象,建立了物理模型和数学模型,对该住宅小区南区四种工况下室外气流流动情况和污染物浓度扩散情况分别进行了三维数值模拟分析,其中以车道中汽车排放的尾气氮氧化物为主要污染源。模拟结果表明:当来流的风速相同时,风向的变化对气流流场的影响是很大的;建筑群周围的绕流过程比单个建筑物更加复杂,除了具有单个建筑物绕流过程中所产生的流动分离和回流等复杂特征外,还存在建筑物之间的互相影响;受风的作用,建筑群周围产生局部湍流,这些湍流区控制着污染物的扩散;在建筑群周围产生湍流和低速区的地方,会出现污染物浓度累积情况。小区内污染物浓度的变化特征是随着离污染源的距离增大逐渐减少,其垂直分布仍符合地面源排放的扩散分布形式;不同风速条件下随风速增大,则污染物散布愈广,相应局部浓度降低。对采样试验结果与相应数值模拟结果进行了对比,两者在趋势上比较一致,通过误差分析,得到采样试验与数值模拟结果的平均偏差仅为0.013mg/m3,平均比例误差仅为0.406,证实了模型的有效性。通过CFD方法对小区气流流动进行模拟仿真,以直观形象的可视化结果展现,氮氧化物的模拟基本上反映了小区整体污染物浓度的变化趋势和特征,模拟结果对于小区布局设计及对小区内环境评价具有一定的参考价值。更多还原

【Abstract】 Ambient air pollution has received more and more attentions in many scientific fields with increasing in urbanization and industrialization in China. Traffic emission is believed as the main air pollution source in the urban environment in current days, it is identified that the automobile exhaust discharges mainly between 0.3~2 meters, and long term exposed to this situation will do harm to people’s health. And the resident district is the main place for people’s living and leisure, to research the pollutant dispersion in the resident district is of great realistic significance.Based on the method of CFD (Computational Fluid Dynamics), the research takes a newly-built resident district in Harbin as the object of numerical simulation and monitoring. After establishing the physical and mathematical model of the resident district, the paper analyzes the airflow and dispersion of vehicle exhaust gas using 3D numerical simulation under four different kinds of states, which considers vehicle exhaust gas (nitrogen oxide) as the main source of pollution.The results show that the state of flow field around building group is different when under the same wind speed and different direction. And the flow process is more complex than the single building, besides all the characteristics such as the breakaway and the backflow, which produces in the single building, but also has mutual influence among the buildings. Around the building group produces partial turbulence, these rapids areas are controlling the pollutant dispersion. In the rapids and the low speed places around the building group, may induce the accumulation of pollutant. Pollutant concentrations will decrease as the distance from measuring point to source increase. Vertical distribution of pollutant concentrations is in accordance with the rules of source on the ground. Pollutant concentrations will spread broadly as the wind speed rise, therewith the local concentrations decrease.Comparing the simulation results with the sampling analysis, it indicates that the simulation value and the monitor value are quite consistent in the tendency, which proves the validity of the model. The error analysis further indicates the tally of monitoring and numerical simulation. The average deviation is only 0.013mg/m3, the average proportional error is only 0.406.Carrying on the numerical simulation through the CFD method to the simulati- on of the district, can provide us a more intuitionistic image and visible result. which can be served for the layout design and environmental assessment more conveniently and effectively. The simulation results made reference to the layout design and environmental evaluation of the resident district.更多还原