主导风向对不规则建筑群街区污染物扩散的影响

Influence of dominant wind direction on traffic pollutant diffusion characteristics in a street canyon with irregular urban building layouts

以城市道路某段典型的街道峡谷为研究对象,采用ICEM CFD数值模拟技术,分析不同风向对不规则建筑群街区污染物扩散影响。结果表明:(1)北风时,距地10.0 m以下范围是污染物高浓度聚集区。与北风工况相比,西北风时街谷内污染物浓度分布变化较大,沿高度截面上升依次呈连续线状→线状和部分团状→断裂团状。(2)随着建筑高度的增加,主干道中的气流绕流作用减弱。通过控制建筑的连续界面诱导街谷中的气流横向绕流,或在临街上游设置合适的开敞空间,以增加来流通风廊道,可有效改善街谷中污染物的扩散。(3)两种风向下每条街道人员停留区内污染物停留时间排序规律相同;不同风向下每条街道人员停留区内污染物停留时间不同,说明风向对每条街道内污染物的影响存在差异,每段街谷内的污染物扩散分布不是孤立系统,而是相互关联的有机整体。

A typical street canyon of a certain section of urban road was taken as the research object,ICEM CFD numerical simulation technology was used to analyze the influence of different wind directions on the pollutants dispersion in irregular building blocks.The results showed that:(1)when the north wind was blown in,a high pollutants concentration area was developed below 10.0 m from the ground.Compared with the north wind conditions,the pollutants concentration distribution in the street canyon changed greatly under the northwest wind.The pollutants distribution in the direction of height cross section was displayed successively linear→linear and partial cluster→fracture cluster.(2)The airflow around the main road was weakened because of the increasing buildings height.And the increasing upstream open space increased the windward area of approaching airflow,so that pollutants dispersion in the street canyon could be improved effectively.(3)The order of pollutant residence time in the people’s stay area of each street under the two wind directions was the same;however,the pollutants residence time in the same area under different wind directions was different.The influence of the wind direction on the pollutants in each street was indicated different.The pollutants dispersion distribution in each street canyon was not an isolated system,but an interrelated organic whole.