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Permanent link (DOI): https://doi.org/10.7939/R3RJ49318

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Buoyancy-Driven Exchange Flow with Applications to Architectural Fluid Mechanics Open Access

Descriptions

Other title
Subject/Keyword
adjacent building zones
Plumes
Gravity current
Natural ventilation
Internal bore
Buoyancy-driven exchange flow
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Nabi, Saleh
Supervisor and department
Dr. Flynn, Morris R (Mechanical Engineering)
Examining committee member and department
Professor Sutherland, Bruce (Physics and Earth and Atmospheric Sciences)
Professor Love, James A (Faculty of Environmental Design)
Professor Koch, C.R. (Bob) (Mechanical Engineering)
Professor Mitra, Sushanta (Mechanical Engineering)
Department
Department of Mechanical Engineering
Specialization

Date accepted
2014-05-14T10:01:53Z
Graduation date
2014-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Buoyancy driven flow between two finite zones containing fluid of slightly different density is investigated. Two zones separated by (i) a single common doorway, and, (ii) top and bottom vents. In the former case, a two-layer exchange flow develops once the barrier is removed. In the zone that initially contained dense fluid, a buoyant plume of light fluid mixes with the dense fluid leading, over time, to the development of non-trivial ambient density stratification. Meanwhile, dense fluid flows as a gravity current into the zone that initially contained light fluid. This gravity current reflects from the end wall and propagates back toward the opening in the form of an internal bore. When the bore reaches the opening the dynamics of the exchange flow are substantially altered. Such coupled dynamics of the two zones are modeled using elements of gravity current, internal bore and plume theory. Depending on the geometric parameters two scenarios are possible. Either the terminal position of the first front lies above the bottom of the barrier, or it lies below. In the latter case, the associated complications are (i) the nature of the exchange flow changes once the downward-propagating first front surpasses the bottom of the barrier, and, (ii) the terminal stratification in the zone that initially contains the light fluid now includes an intermediate layer. We also present a model that presumes that both zones remain well-mixed. When the two zones are separated by top and bottom vents, two oppositely directed exchange flows are generated. The transient evolution of the interface, stratification and buoyancy in each zone are estimated both for the case where the light zone does and does not contain a source of buoyancy. Attention is focused on the influence of the effective area, source buoyancy flux and the time during which the source is switched on. Similitude experiments help to identify the limitations of the analytical models for each scenario. The implications of our results on the design of multi-zone buildings that exploit passive heat gains are also discussed.
Language
English
DOI
doi:10.7939/R3RJ49318
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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