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Experimental investigation of near-field stream-wise flow development and spatial structure in triple buoyant plumes
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
2019 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 149, p. 79-89Article in journal (Refereed) Published
Abstract [en]

This paper presents a systematic experimental study on stream-wise flow development and spatial structure of triple buoyant plumes. Two-dimensional Particle Image Velocimetry (2-D PIV) is employed to resolve velocity fields. Stream-wise axial velocity profiles, flow structure, flow region parameters, and self-similarity properties are analyzed at different configurations that are characterized by spacing ratios S/W (source spacing S divided by source width W). From velocity fields and axial velocity profiles, a similar stream-wise developing trend is identified in different source configurations. When near-field plumes travel downstream, axial velocities increase rapidly, off-center velocity peaks get merged with the central peak, and the number of velocity peaks reduces with the downstream distance. A compact source layout, comparing with the wide one, could enhance the near-field plumes interaction and promote the plumes deflection significantly. Fundamentally, the stream-wise spatial structure of the triple plumes initially consists of a converging region, followed by a merging region, and finally a combined region. By examining the averaged velocity fields, flow recirculation with negative axial velocities is found to scarcely exist in the converging region. Merging level Zm and quasi-combined level Zqc are analyzed quantitatively and statistically. Within the studied S/W range, the normalized Zm shows a linear increase with S/W in the formula of Zm/H=2.007(S/W)+1.173 and the normalized Zqc gives a power law increase with S/W in the formula of Zqc/H=6.035(S/W)0.4959. In addition, triple plumes are found to establish self-similarity approximately at Z = 3H with S/W of 0.2 and at Z = 4.5H with S/W of 0.5.

Place, publisher, year, edition, pages
Elsevier Ltd , 2019. Vol. 149, p. 79-89
Keywords [en]
Merging level, Quasi-combined level, Self-similarity, Source spacing, Spatial structure, Stream-wise flow development, Merging, Velocity, Velocity measurement, Flow development, Self-similarities, Buoyancy
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:hig:diva-29063DOI: 10.1016/j.buildenv.2018.11.039ISI: 000457118300008Scopus ID: 2-s2.0-85058185482OAI: oai:DiVA.org:hig-29063DiVA, id: diva2:1275821
Note

Funding Agency:

RGC GRF project of the Hong Kong SAR Government  Grant no: 17201817

Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-03-12Bibliographically approved

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Sandberg, Mats

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