On the wind flow patterns under neutral and unstable conditions in an urban area

Nezis, AA; Angelidis, DI; Assimakopoulos, VD; Bergeles, GC

dc.contributor.author	Nezis, AA	en
dc.contributor.author	Angelidis, DI	en
dc.contributor.author	Assimakopoulos, VD	en
dc.contributor.author	Bergeles, GC	en
dc.date.accessioned	2014-03-01T02:51:46Z
dc.date.available	2014-03-01T02:51:46Z
dc.date.issued	2008	en
dc.identifier.issn	13300083	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/35640
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-56349155068&partnerID=40&md5=35614dfeca579620d93bdb8dfad0b27a	en
dc.subject	Pollutant dispersion	en
dc.subject	Street canyon	en
dc.subject	Unstable stratification	en
dc.subject	Unstructured Cartesian grid	en
dc.subject	Wind tunnel	en
dc.subject.other	air quality	en
dc.subject.other	anemometer	en
dc.subject.other	computational fluid dynamics	en
dc.subject.other	conference proceeding	en
dc.subject.other	experimental study	en
dc.subject.other	flow field	en
dc.subject.other	flow pattern	en
dc.subject.other	measurement method	en
dc.subject.other	Navier-Stokes equations	en
dc.subject.other	numerical method	en
dc.subject.other	street canyon	en
dc.subject.other	turbulence	en
dc.subject.other	wind direction	en
dc.subject.other	wind tunnel	en
dc.subject.other	wind velocity	en
dc.title	On the wind flow patterns under neutral and unstable conditions in an urban area	en
heal.type	conferenceItem	en
heal.publicationDate	2008	en
heal.abstract	Wind flow, turbulence and pollutant dispersion characteristics within an urban street canyon depend largely on the thermal behaviour of the materials, e.g., the street floor under the sun and on the geometrical characteristics of the surrounding buildings under low wind conditions. They have a detrimental effect on the stability conditions within and above street canyons, which in turn affect the wind flow patterns and the local air quality. The purpose of the present work is to study experimentally and numerically the flow field developed under neutral and unstable stratification conditions within a typical square urban street canyon. A two-dimensional set up is employed including several canyons in order to simulate an urban environment. Experiments were carried out with the use of a triple hot sensor anemometer upwind above and downwind an isolated building. Measurements were taken under neutral stratification conditions for a wind speed of 3ms-1. Two dimensional numerical simulations have also been conducted for typical urban street canyons. The numerical results have been obtained by the solution of the time averaged Navier-Stokes equations coupled with the standard k-ε turbulence model. The performance of the CFD algorithm is increased by the unstructured Cartesian grid. The numerical code was firstly validated with the experimental results derived under neutral stratification conditions. The effects of stability within a typical urban area were also studied numerically. Spatial distributions of wind velocity, turbulence and pollutants, within street canyons, were analyzed under neutral and unstable conditions for Richardson number Rb=0.17. Under unstable conditions a great deal of mixing exists within the street canyons. The buoyancy induced flow affects the air exchange between the street canyons and the free surface layer. Vertical air motions extend beyond the level of the street canyons causing instability to increase. It was found, that the stratification effects on the flow can be successfully predicted by the CFD numerical code.	en
heal.journalName	Hrvatski Meteoroloski Casopis	en
dc.identifier.volume	43 PART 2	en
dc.identifier.spage	643	en
dc.identifier.epage	647	en