基于RANS的城市广场空气质量评价及健康场所指引

空气中污染物及病菌的浓度直接影响人类健康。在污染源不变的情况下,有效通风决定了空气质量的优劣。因此,建立有效通风的定量判定指标,并利用此指标对特定区域空气质量进行实时评价,引导居民选择健康的室外活动场所成为迫切需要解决的问题。本研究采用雷诺平均Navier-Stokes(RANS)方法建立了基于计算流体力学(CFD)技术的城市空气污染模拟系统,研究了风速、污染物浓度和污染物扩散效率之间的关系。在此基础上,借助实时气象数据,对城市广场空间不同时段进行了风场模拟及空气质量评价。结果表明: 行人高度(1.5 m)空气中污染物有效扩散的临界风速值为1.0 m·s^-1,此指标可作为某一具体区域空气质量评价标准。参照此判定指标,链接实时天气系统,通过模拟得到的行人高度风速分布,可实时、可视化地显示该场所空气质量优劣分布,实现公平、效率、合理地利用城市空间资源,为人们选择健康的室外活动场地提供指引,为公众疾病预防和健康促进提供技术和手段。

Air quality assessment and health site guidelines for city squares based on RANS method

The concentration of pollutants and pathogens in the air directly affects human health. When the pollution source remains unchanged, effective ventilation determines air quality. It is therefore critically needed to establish a quantitative determination index for effective ventilation, which can be used for real-time evaluation of air quality in specific areas, so as to guide residents to choose healthy outdoor activity places. In this study, Reynolds average Navier-Stokes (RANS) method was used to establish urban air pollution simulation system by computational fluid dynamics (CFD) technology. The correlations among wind speed, pollutant concentration, and pollutant diffusion efficiency were analyzed. With real-time meteorological data, wind field simulation and air quality evaluation were carried out for different periods of urban square space. The results showed that the critical wind speed value at pedestrian height (1.5 m) for the effective diffusion of pollutants was 1.0 m·s^-1, which could be used as an air quality evaluation standard. With reference to this judgment index and the real-time weather system link, the pedestrian height wind speed distribution could be obtained through simulation. Therefore, the spatial variation of air quality could be visually displayed in real time, which help realize fair, efficient and reasonable use of urban space resources. This work could provide guidelines for choosing healthy outdoor venues, and provide technologies and means for public disease prevention and health promotion.