高层建筑群对街谷内颗粒物扩散特性的影响
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摘要
为了获得城市冠层内高层建筑群的高度变化对城市颗粒物污染的作用情况,采用大涡模拟方法研究了不同高层建筑群的街谷形状因子对街谷内空气流动与污染物扩散规律的影响。结果表明:在高层建筑群上方形成一个顺时针旋涡,旋涡中心位于城市峡谷内靠近高层建筑群背风处;随着街谷形状因子的增大,高层建筑群的滞留效应增强,导致高层建筑物上方的剪切层湍动能增强;当形状因子为2.5时,湍动能达到1.9 m~2·s~(-2),此时城市街谷内可吸入颗粒物的稀释扩散条件变差;在涡旋和气流夹带作用下,可吸入颗粒物浓度在垂直方向上分布具有明显的分层现象,大量可吸入颗粒物聚集于低建筑迎风面底部。不同街谷形状因子下街谷内空气流动与污染物扩散规律的探明将为有关部门制定相应规划提供参考。
In order to obtain the effects of height variation of high-rise buildings in urban canopy on theparticulate pollution, large-eddy simulation was used to study the influence of street shape factors of differenthigh-rise buildings on airflow and pollutant diffusion in the canyon. The simulation result shows that a clockwisevortex could be formed above the high-rise buildings, and its center is located near the lee of the high-risebuildings in the urban canyon. With the increase of the shape factor of the valley, the particulate-retention effectof the high-rise buildings will increase, which could strengthen the turbulent kinetic energy and air stagnation ofthe shear layer above the building. The dilution and diffusion conditions of the inhalable particles in the urbanstreet canyon become worse at the shape factor of 2.5 and the turbulent kinetic energy is 1.9 m~2·s~(-2). With theentrainment of the vortex and the airflow, an obvious concentration stratification distribution will occur in thevertical direction for the inhalable particulates, a large number of them will gather at the bottom of windwardside of the low-rise buildings. To achieve the spread of particulate pollutants outside the urban street canyon, itis necessary to observe the law of airflow and pollutant diffusion with different aspect ratio, which will provide atheoretical basis for relevant government departments to formulate the corresponding policies and regulations.
In order to obtain the effects of height variation of high-rise buildings in urban canopy on theparticulate pollution, large-eddy simulation was used to study the influence of street shape factors of differenthigh-rise buildings on airflow and pollutant diffusion in the canyon. The simulation result shows that a clockwisevortex could be formed above the high-rise buildings, and its center is located near the lee of the high-risebuildings in the urban canyon. With the increase of the shape factor of the valley, the particulate-retention effectof the high-rise buildings will increase, which could strengthen the turbulent kinetic energy and air stagnation ofthe shear layer above the building. The dilution and diffusion conditions of the inhalable particles in the urbanstreet canyon become worse at the shape factor of 2.5 and the turbulent kinetic energy is 1.9 m~2·s~(-2). With theentrainment of the vortex and the airflow, an obvious concentration stratification distribution will occur in thevertical direction for the inhalable particulates, a large number of them will gather at the bottom of windwardside of the low-rise buildings. To achieve the spread of particulate pollutants outside the urban street canyon, itis necessary to observe the law of airflow and pollutant diffusion with different aspect ratio, which will provide atheoretical basis for relevant government departments to formulate the corresponding policies and regulations.
引文
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[18]DAVIDSON M J,MYLNE K R,JONES C D,et al.Plume dispersion through large groups of obstacles:A field investigation[J].Atmospheric Environment,1995,29(22):3245-3256.
[2]冯寒立,赵敬德,翟静.高架覆盖的街谷内可吸入颗粒物的浓度分布[J].环境工程学报,2017,11(8):4669-4676.
[3]白志鹏,张文杰,韩斌,等.我国环境空气颗粒物质量基准研究框架及研究体系的构建[J].环境科学研究,2015,28(5):667-675.
[4]DONG J,TAN Z,XIAO Y,et al.Seasonal changing effect on airflow and pollutant dispersion characteristics in urban street canyons[J].Atmosphere,2017,8(43):1-18.
[5]张传福,曾建荣,文谋,等.高架桥对街道峡谷内大气颗粒物输运的影响[J].环境科学研究,2012,25(2):159-164.
[6]JICHA M,KATOLICKY J,POSPISIL J.Dispersion of pollutants in a street canyon and street intersection under traffic-induced flow and turbulence using a low Re k-εmodel[J].International Journal of Environment and Pollution,2002,18(2):160-170.
[7]XIE X M,HUANG Z,WANG J S.Impact of building configuration on air quality in street canyon[J].Atmospheric Environment,2005,39(25):4519-4530.
[8]XIE X M,HUANG Z,WANG J S,et al.The impact of solar radiation and street layout on pollutant dispersion in street canyon[J].Building and Environment,2005,40(2):201-212.
[9]RAMAMURTHY P,PARDYJAK E R,KLEWICKI J C.Observations of the effects of atmospheric stability on turbulence statistics deep within an urban street canyon[J].Journal of Applied Meteorology&Climatology,2007,46(12):2074-2085.
[10]GU Z L,ZHANG Y W,CHENG Y,et al.Effect of uneven building layout on air flow and pollutant dispersion in non-uniform street canyons[J].Building&Environment,2011,46(12):2657-2665.
[11]WANG L,PAN Q,ZHENG X P,et al.Effects of low boundary walls under dynamic inflow on flow field and pollutant dispersion in an idealized street canyon[J].Atmospheric Pollution Research,2017,8(3):564-575.
[12]MARCOS MáP,FEIJó-MU?OZ J,MEISS A.Wind velocity effects on the quality and efficiency of ventilation in the modeling of outdoor spaces:Case studies[J].Building Services Engineering Research&Technology,2015,37(1):2661-2665.
[13]MOCHIDA A,TOMINAGA,YOSHIHIDE,et al.Comparison of various k-εmodels and DSM applied to flow around a high-rise building:Report on AIJ cooperative project for CFD prediction of wind environment[J].Wind and Structures,2002,5(2/3/4):227-244.
[14]张云伟,王晴茹,陈嘉,等.城市街谷内PM2.5浓度时空变化及影响因素分析[J].中国环境科学,2016,36(10):2944-2949.
[15]陈晓萌,亢燕铭,杨方,等.上游阻挡建筑间距对街谷内空气环境的影响[J].中国环境科学,2016,36(7):1967-1973.
[16]陈巨辉.基于大涡模拟:颗粒二阶矩的两相流动与反应数值模拟[D].哈尔滨:哈尔滨工业大学,2013.
[17]赵宝芹,王嘉松,汪立敏,等.城市对称街道峡谷气流及污染物扩散特征的研究[J].水动力学研究与进展,2005,20(5):610-615.
[18]DAVIDSON M J,MYLNE K R,JONES C D,et al.Plume dispersion through large groups of obstacles:A field investigation[J].Atmospheric Environment,1995,29(22):3245-3256.
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