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Article: Mean shear flow in recirculating turbulent urban convection and the plume-puff eddy structure below stably stratified inversion layers

TitleMean shear flow in recirculating turbulent urban convection and the plume-puff eddy structure below stably stratified inversion layers
Authors
Keywordsatmospheric convection
atmospheric structure
convective boundary layer
rmixed layer
shear flow
Issue Date2019
PublisherSpringer-Verlag Wien. The Journal's web site is located at http://www.springer.at/tac
Citation
Theoretical and Applied Climatology, 2019, v. 135 n. 3-4, p. 1485-1499 How to Cite?
AbstractThe mean and random components of the velocity field at very low wind speeds in a convective boundary layer (CBL) over a wide urban area are dominated by large eddy structures—either turbulent plumes or puffs. In the mixed layer at either side of the edges of urban areas, local mean recirculating flows are generated by sharp horizontal temperature gradients. These recirculation regions also control the mean shear profile and the bent-over plumes across the mixed layer, extending from the edge to the center of the urban area. A simplified physical model was proposed to calculate the mean flow speed at the edges of urban areas. Water tank experiments were carried out to study the mean recirculating flow and turbulent plume structures. The mean speed at urban edges was measured by the particle image velocimetry (PIV), and the plume structures were visualized by the thermalchromic liquid crystal (TLC) sheets. The horizontal velocity calculated by the physical model at the urban edge agrees well with that measured in the water tank experiments, with a root mean square of 0.03. The experiments also show that the pattern of the mean flow over the urban area changes significantly if the shape of the heated area changes or if the form of the heated urban area becomes sub-divided, for example by the creation of nearby but separated “satellite cities.” The convective flow over the square urban area is characterized as the diagonal inflow at the lower level and the side outflow at the upper level. The outflow of the small city can be drawn into the inflow region of the large city in the “satellite city” case. A conceptual analysis shows how these changes significantly affect the patterns of dispersion of pollutants in different types of urban areas.
Persistent Identifierhttp://hdl.handle.net/10722/278214
ISSN
2017 Impact Factor: 2.321
2015 SCImago Journal Rankings: 1.030

 

DC FieldValueLanguage
dc.contributor.authorFAN, Y-
dc.contributor.authorHunt, J-
dc.contributor.authorYIN, S-
dc.contributor.authorLi, Y-
dc.date.accessioned2019-10-04T08:09:41Z-
dc.date.available2019-10-04T08:09:41Z-
dc.date.issued2019-
dc.identifier.citationTheoretical and Applied Climatology, 2019, v. 135 n. 3-4, p. 1485-1499-
dc.identifier.issn0177-798X-
dc.identifier.urihttp://hdl.handle.net/10722/278214-
dc.description.abstractThe mean and random components of the velocity field at very low wind speeds in a convective boundary layer (CBL) over a wide urban area are dominated by large eddy structures—either turbulent plumes or puffs. In the mixed layer at either side of the edges of urban areas, local mean recirculating flows are generated by sharp horizontal temperature gradients. These recirculation regions also control the mean shear profile and the bent-over plumes across the mixed layer, extending from the edge to the center of the urban area. A simplified physical model was proposed to calculate the mean flow speed at the edges of urban areas. Water tank experiments were carried out to study the mean recirculating flow and turbulent plume structures. The mean speed at urban edges was measured by the particle image velocimetry (PIV), and the plume structures were visualized by the thermalchromic liquid crystal (TLC) sheets. The horizontal velocity calculated by the physical model at the urban edge agrees well with that measured in the water tank experiments, with a root mean square of 0.03. The experiments also show that the pattern of the mean flow over the urban area changes significantly if the shape of the heated area changes or if the form of the heated urban area becomes sub-divided, for example by the creation of nearby but separated “satellite cities.” The convective flow over the square urban area is characterized as the diagonal inflow at the lower level and the side outflow at the upper level. The outflow of the small city can be drawn into the inflow region of the large city in the “satellite city” case. A conceptual analysis shows how these changes significantly affect the patterns of dispersion of pollutants in different types of urban areas.-
dc.languageeng-
dc.publisherSpringer-Verlag Wien. The Journal's web site is located at http://www.springer.at/tac-
dc.relation.ispartofTheoretical and Applied Climatology-
dc.rightsThis is a post-peer-review, pre-copyedit version of an article published in [insert journal title]. The final authenticated version is available online at: http://dx.doi.org/[insert DOI]-
dc.subjectatmospheric convection-
dc.subjectatmospheric structure-
dc.subjectconvective boundary layer-
dc.subjectrmixed layer-
dc.subjectshear flow-
dc.titleMean shear flow in recirculating turbulent urban convection and the plume-puff eddy structure below stably stratified inversion layers-
dc.typeArticle-
dc.identifier.emailLi, Y: liyg@hku.hk-
dc.identifier.authorityLi, Y=rp00151-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1007/s00704-018-2458-9-
dc.identifier.scopuseid_2-s2.0-85044054957-
dc.identifier.hkuros306623-
dc.identifier.volume135-
dc.identifier.issue3-4-
dc.identifier.spage1485-
dc.identifier.epage1499-
dc.publisher.placeAustria-

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