StudyoninfluenceofviaductandnoisebarriersontheparticulatematterdispersioninstreetcanyonsbyCFDmodeling

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Thispaperinvestigatestheinfluenceofviaduct,noisebarrier,andtheratioofleewardandwindwardbuildingheight (H1/H2) on flow regime and particulate matters (PM) dispersion in an urban street canyon, usingComputational Fluid Dynamic (CFD) simulation. Results show that viaduct introduces more sources of parti-culate andinfluences the flow pattern significantly. New vortexes form whennoise barriers set up along theviaductandinfluencetheflowaroundtheviaductanddistributionofpollutantsatthecenterofthecanyonbutinfluencetoalessextentinthekeybreathingzones.Whenthestreetcanyonissymmetric,barrierscanreducethepeakvalueofpollutantconcentrationatbuildingswall,andlowertheintegralconcentrationinzonesthataffect people's breathing. When the street canyon is a step-up type (the leeward building is lower than thewindward one), barriers affect to a less extent the PM distributions at buildings wall and breathing zones.Increaseoftheheightofwindwardbuildingshindersthediffusionofpollutants.Furthermore,peoplelivinginthewindwardbuildingorwalkingonthestreethavetosuffermorefromthepollutant.Whenthestreetcanyonisastep-downtype(theleewardbuildingishigherthanthewindwardone),H1/H2=6/5,pollutantsstillgatherattheleewardwall.Ithastheleastintegralpollutantconcentrationinthezonenearbuildingsandstreet.H1/H2=2,pollutantsaretransportedtothewindwardwallandaccumulatedbecauseoftheuppermainvortexinthecanyon.Pedestrians'breathingzoneisextremelyhighcomparedwithotherconfigurations.