T型街道内空气流动与污染物扩散特性研究
|
摘要
为研究T型街道峡谷内空气流动与污染物扩散传质的特性,利用数值模拟研究来流风向角(θ)的变化(θ为45°、90°和135°)对T型街道交叉路口内空气流动与机动车尾气污染物扩散传递的影响,并与风洞实验测量数据进行验证。3种湍流模型中,可实现k—ε模型计算的速度相对偏差小于8%,与风洞实验结果一致性最好。结果表明,来流风向角的变化,会造成从街道顶部或侧面进入街道内的气流方向及通量发生改变,从而显著影响T型街道交叉口内及其附近的流动结构和污染物浓度分布。污染物容易在建筑尾流区等流动不畅的区域产生聚集,造成污染浓度偏高。当θ=135°时,T型街道内通风条件最好,街道内行人呼吸高度和建筑临街立面附近污染物浓度水平均相对较低。由于流动结构的改善,T型街道峡谷内的污染水平低于一般街道峡谷。
To investigate the characteristics of air flow and pollutant dispersion in T type street canyon,numerical simulation validated by wind-tunnel experiments had been conducted to study the effect of inflow angles(θof 45°,90°and 135°)on the mean wind flow and pollutant dispersion in T type street canyon.The comparison of velocity distribution among three turbulence models and wind-tunnel measurements indicated that numerical results from the realizable k-εturbulence model matched closely with the wind-tunnel measurements with less than 8%relative deviation for the mean velocity.The results showed that the changing inflow direction angle would cause the major variation of the flow direction and flux of the inflow air from the top and side of the building,thereby affect the flow structure and the pollutant diffusion in T type street canyon notably.Moreover,it would impede the airflow to easily cause accumulation of the pollutants in the areas of vortex generation,and then lead to a high level of pollutant concentration.Whenθ=135°,he better ventilation condition brought about a lower pollutant concentration level both on the respiratory plane and vertical faade near street.In addition,due to the improvement on flow structure,the studied T type street canyon kept a lower pollution level than the general street canyon.
To investigate the characteristics of air flow and pollutant dispersion in T type street canyon,numerical simulation validated by wind-tunnel experiments had been conducted to study the effect of inflow angles(θof 45°,90°and 135°)on the mean wind flow and pollutant dispersion in T type street canyon.The comparison of velocity distribution among three turbulence models and wind-tunnel measurements indicated that numerical results from the realizable k-εturbulence model matched closely with the wind-tunnel measurements with less than 8%relative deviation for the mean velocity.The results showed that the changing inflow direction angle would cause the major variation of the flow direction and flux of the inflow air from the top and side of the building,thereby affect the flow structure and the pollutant diffusion in T type street canyon notably.Moreover,it would impede the airflow to easily cause accumulation of the pollutants in the areas of vortex generation,and then lead to a high level of pollutant concentration.Whenθ=135°,he better ventilation condition brought about a lower pollutant concentration level both on the respiratory plane and vertical faade near street.In addition,due to the improvement on flow structure,the studied T type street canyon kept a lower pollution level than the general street canyon.
引文
[1]孙文文,江洪,陈洪滨,等.北京地区大气气溶胶光学特性与区域雾霾事件分析[J].环境污染与防治,2016,38(2):1-6,12.
[2]AI Z T,MAK C M.From street canyon microclimate to indoor environmental quality in naturally ventilated urban buildings:issues and possibilities for improvement[J].Building and Environment,2015,94(2):489-503.
[3]TIWARY A,ROBINS A,NAMDEO A,et al.Air flow and concentration fields at urban road intersections for improved understanding of personal exposure[J].Environment International,2011,37(5):1005-1018.
[4]黄远东,王守生,金鑫,等.城市街道峡谷内污染物扩散模拟中不同湍流模型的比较研究[J].水动力学研究与进展,2008,23(2):189-195.
[5]SAATHOFF P,GUPTA A,STATHOPOULOS T,et al.Contamination of fresh air intakes due to downwash from a rooftop structure[J].Journal of the Air&Waste Management Association,2009,59(3):343-353.
[6]蒋德海,蒋维楣,苗世光.城市街道峡谷气流和污染物分布的数值模拟[J].环境科学研究,2006,19(3):7-12.
[7]DOBRE A,ARNOLD S J,SMALLEY R J,et al.Flow field measurements in the proximity of an urban intersection in London,UK[J].Atmospheric Environment,2005,39(26):4647-4657.
[8]程云章,黄远东,李文孟.城市街道峡谷内污染物扩散分布的数值模拟[J].环境科学与技术,2009,32(8):183-186.
[9]TOMINAGA Y,MOCHIDA A,YOSHIE R A,et al.AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings[J].Journal of Wind Engineering and Industrial Aerodynamics,2008,96(10/11):1749-1761.
[10]陶文铨.数值传热学[M].2版.西安:西安交通大学出版社,2001.
[11]DI SABATINO S,BUCCOLIERI R,PULVIRENTI B,et al.Flow and pollutant dispersion in street canyons using FLUENT and ADMS-Urban[J].Environmental Modeling&Assessment,2008,13(3):369-381.
[12]徐伟嘉,余志,蔡铭,等.街道峡谷内不同车道污染物扩散的数值模拟[J].环境科学研究,2010,23(8):1007-1012.
[2]AI Z T,MAK C M.From street canyon microclimate to indoor environmental quality in naturally ventilated urban buildings:issues and possibilities for improvement[J].Building and Environment,2015,94(2):489-503.
[3]TIWARY A,ROBINS A,NAMDEO A,et al.Air flow and concentration fields at urban road intersections for improved understanding of personal exposure[J].Environment International,2011,37(5):1005-1018.
[4]黄远东,王守生,金鑫,等.城市街道峡谷内污染物扩散模拟中不同湍流模型的比较研究[J].水动力学研究与进展,2008,23(2):189-195.
[5]SAATHOFF P,GUPTA A,STATHOPOULOS T,et al.Contamination of fresh air intakes due to downwash from a rooftop structure[J].Journal of the Air&Waste Management Association,2009,59(3):343-353.
[6]蒋德海,蒋维楣,苗世光.城市街道峡谷气流和污染物分布的数值模拟[J].环境科学研究,2006,19(3):7-12.
[7]DOBRE A,ARNOLD S J,SMALLEY R J,et al.Flow field measurements in the proximity of an urban intersection in London,UK[J].Atmospheric Environment,2005,39(26):4647-4657.
[8]程云章,黄远东,李文孟.城市街道峡谷内污染物扩散分布的数值模拟[J].环境科学与技术,2009,32(8):183-186.
[9]TOMINAGA Y,MOCHIDA A,YOSHIE R A,et al.AIJ guidelines for practical applications of CFD to pedestrian wind environment around buildings[J].Journal of Wind Engineering and Industrial Aerodynamics,2008,96(10/11):1749-1761.
[10]陶文铨.数值传热学[M].2版.西安:西安交通大学出版社,2001.
[11]DI SABATINO S,BUCCOLIERI R,PULVIRENTI B,et al.Flow and pollutant dispersion in street canyons using FLUENT and ADMS-Urban[J].Environmental Modeling&Assessment,2008,13(3):369-381.
[12]徐伟嘉,余志,蔡铭,等.街道峡谷内不同车道污染物扩散的数值模拟[J].环境科学研究,2010,23(8):1007-1012.