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CFD and wind-tunnel analysis of outdoor ventilation in a real compact heterogeneous urban area: Evaluation using “air delay”
Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus; Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands.
Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands; Department of Civil Engineering, KU Leuven, Leuven, Belgium.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. (Inomhusmiljö)
Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus.
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2017 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 126, 355-372 p.Article in journal (Refereed) Published
Abstract [en]

Outdoor urban ventilation in a real complex urban area is investigated by introducing a new ventilation indicator – the "air delay". Computational Fluid Dynamics (CFD) simulations are performed using the 3D steady Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The up-to-date literature shows the lack of detailed evaluations of the two approaches for real compact urban areas. This study further presents a systematic evaluation of steady RANS and LES for the assessment of the ventilation conditions in a dense district in Nicosia, Cyprus. The ventilation conditions within the urban area are investigated by calculating the distribution of the age of air. To better assess the outdoor ventilation, a new indicator, the "air delay" is introduced as the difference between the local mean age of air at an urban area and that in an empty domain with the same computational settings, allowing the comparison of the results in different parts of the domain, without impact of the boundary conditions. CFD results are validated using wind-tunnel measurements of mean wind speed and turbulence intensity performed for the same urban area. The results show that LES can accurately predict the mean wind speed and turbulence intensity with the average deviations of about 6% and 14%, respectively, from the wind-tunnel measurements while for the steady RANS, these are 8% and 31%, respectively. The steady RANS simulations overestimate the local mean air delay. The deviation between the two approaches is 52% at pedestrian level (2 m).

Place, publisher, year, edition, pages
2017. Vol. 126, 355-372 p.
Keyword [en]
Air delay, City breathability, Computational Fluid Dynamics (CFD), Large Eddy Simulations (LES), Steady RANS, Urban microclimate
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:hig:diva-25585DOI: 10.1016/j.buildenv.2017.10.013OAI: oai:DiVA.org:hig-25585DiVA: diva2:1159964
Available from: 2017-11-24 Created: 2017-11-24 Last updated: 2017-12-06Bibliographically approved

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