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《道路绿化带对街道峡谷内污染物扩散的影响研究.pdf》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、第33卷第2期Vo1.33,No.2环境科学2012年2月Feb.,2012ENVIR0NMENTALSCIENCE道路绿化带对街道峡谷内污染物扩散的影响研究徐伟嘉,幸鸿,余志(1.中山大学先进技术研究院,广州510275;2.中山大学工学院,广东省智能交通系统重点实验室,广州510275;3.东莞中山大学研究院,东莞523808)摘要:研究了道路绿化带对街道峡谷内流场与机动车尾气扩散的影响特征.假设绿化带树冠为均匀多孔介质,采用压力损失系数表征树冠对空气流动的阻碍作用,建立可用于数值模拟的绿化带多孑L介质物理模型.采用稳态k-6湍流模型结合组分输运方程模
2、拟道路中央有绿化带街道峡谷内的尾气扩散过程,模拟结果与风洞试验数据对比吻合较好.分析发现,有绿化带街道峡谷内存在一个围绕树冠的顺时针旋涡,旋涡中心略偏向右上方,背风面污染物浓度显著增大,较无绿化带的污染物平均浓度增长46.0%.进一步模拟了不同绿化带树冠高度情况下街道峡谷内流场与浓度场,发现随着树冠位置的上升,峡谷内流场旋涡中心逐步上移且偏向迎风建筑物,峡谷内整体气流速度下降,污染物浓度逐步升高,树冠底部高度为8m时其污染物浓度可达4m时的2倍多;尤其是当树冠顶部超过屋顶高度时,峡谷内污染物总体浓度增长迅速.关键词:街道峡谷;绿化带;多孔介质;污染物扩散;
3、数值模拟中图分类号:X511文献标识码:A文章编号:0250.330l(2012)02.0532.07Effect0fGreenbelt0nPollutantDispersioninStreetCanyonXUWei.iia,XINGHong,YUZhi(1.InstituteofAdvancedTechnology,SunYat—senUniversity,Guangzhou510275,China;2.GuangdongProvincialKeyLaboratoryofIntelligentTransportationSystem,SchoolofEn
4、gineering,SunYat·senUniversity,Guangzhou510275,China;3.InstituteofDongguan—SunYat—senUniversity,Dongguan523808,China)Abstract:Theefectfeatureofgreenbeltonflowfieldandpollutantdispersioninurbanstreetcanyonwasresearched.Thegreenbeltwasassumedasuniformporousmediaanditsaerodynamicspro
5、pertydefinedbythepressurelosscoeficient.Subsequently,thepollutantdispersioninthestreetcanyonofwhichtherewasgreenbeltinthemiddlewassimulatedwiththesteady—statestandardk—sturbulencemodelandspeciestransportequation.Thesimulatedresuhsagreedwellwiththewind-tunneldata.Comparedwiththetre
6、elesscase,itfindsthatthestreetcanyoncontainaclockwisevortex,thepollutantconcentrationoftheleewardwasseveraltimesthanthewindwardandthegrowthrateofpollutantconcentrationwas46.O%.Thefurthersimulationfortheimpactoftreecrownpositionontheairflowandpollutantdispersionfindsthattheheightof
7、majorvortexcenterinthestreetcanyonincreaseswiththeheightoftreecrownandgraduallyclosesthetopofwindwardbuildingThiscausesthattheaveragewindspeedinthestreetcanyondecreases.Especiallywhenthetopoftreecrownovertheroofandhindertheairflowabovethestreetcanyon,theaveragepollutantconcentrati
8、onincreaseswiththeheightoftreecro
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