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The effect of building spacing on near-field temporal evolution of triple building plumes
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
2017 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 122, 35-49 p.Article in journal (Refereed) Published
Abstract [en]

Building plume is important for ventilation and pollutants dispersion along and above buildings in an urban canopy layer. This study fundamentally explores the merging process and temporal penetration of triple uniformly distributed starting building plumes, with a focus of the spacing effect on near-field flow dynamics. Instantaneous velocity and vorticity distributions, penetrating velocities, and stream-wise penetrated heights are quantitatively examined using 2-D particle image velocimetry (PIV) measurements at spacing ratios S/W (building spacing/building width) of 0.2, 0.5, and 1.0. We identified a four-stage merging progress and captured three main spacing-induced merging features. A compact layout at S/W = 0.2 introduces a strong upward channel flow. The wall flows beside the channel tend to draw together first and the unstable channel flow determines the flow pattern transition. In contrast, wider layouts at S/W = 0.5 and 1.0 exhibit intensive downward flow. The wall flows tend to exhibit self-merging initially and the downstream natural swaying motion dominates the merged pattern variations. Merging effect and buoyancy force jointly determine the temporal penetrating velocities. Temporal series of maximum axial velocities above the middle source fits into a power law profile at S/W = 0.2 but a linear function of time at S/W = 0.5 and 1.0. The normalized penetrated heights at S/W = 1.0 are notably faster than in the other two cases before the normalized time is at 3.00 probably because the weaker entrainment and interaction with neighbors lead to less energy and momentum dissipation, quicker self-merging, and faster penetration.

Place, publisher, year, edition, pages
2017. Vol. 122, 35-49 p.
Keyword [en]
Merging feature, PIV measurement, Spacing, Temporal penetration, Thermal-induced city ventilation, Triple pure plumes, Buildings, Buoyancy, Channel flow, Flow patterns, Merging, Velocity, Velocity measurement, Wall flow, Flow pattern transition, Particle image velocimetries, PIV measurements, Pollutants dispersions, Vorticity distribution, Walls (structural partitions)
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:hig:diva-24881DOI: 10.1016/j.buildenv.2017.05.030ISI: 000407184400004Scopus ID: 2-s2.0-85020251852OAI: oai:DiVA.org:hig-24881DiVA: diva2:1134143
Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2017-12-06Bibliographically approved

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