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Permanent link (DOI): https://doi.org/10.7939/R38D1V

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Air Injection for River Water Quality Improvement Open Access

Descriptions

Other title
Subject/Keyword
Transverse mixing
Dissolved oxygen
Rivers
Effluent mixing
Bubbly jets
River discharge
Air/oxygen injection
Crossflow
Bubble plumes
Dye test
Multiport diffusers
Ice cover
Plumes
Jets
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Zhang, Wenming
Supervisor and department
Zhu, David Z. (Civil and Environmental Engineering)
Examining committee member and department
Yu, Tong (Civil and Environmental Engineering)
Fleck, Brian (Mechanical Engineering)
Zhu, David Z. (Civil and Environmental Engineering)
Gulliver, John S. (Civil Engineering, University of Minnesota)
Rajaratnam, Nallamuthu (Civil and Environmental Engineering)
Department
Department of Civil and Environmental Engineering
Specialization
Water Resources Engineering
Date accepted
2012-08-02T10:31:07Z
Graduation date
2012-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
The problem of low dissolved oxygen (DO) level has been found to be widespread in ice-covered or polluted rivers. This thesis is targeted at providing some fundamental studies on the remediation measure of injecting air/oxygen via existing effluent diffusers to increase river’s DO level, with two main focuses: effluent mixing from multiport diffusers and bubbly jets in crossflows. A comprehensive literature review was first provided on transport of conservative chemicals with jets and plumes in the environment. Effluent mixing in rivers was studied based on a field dye test, and the mixing was further divided into near-field and far-field mixing. In the near-field (within the vertically fully mixed distance), effluent mixing from a multiport diffuser was studied in four zones: free jet zone, jet surface impingement zone, merging zone and river vertical mixing zone. The applicability of prevailing models for multiport diffusers was examined. In the far-field, river transverse mixing dominates further mixing of effluent. A modified streamtube method was proposed to describe transverse mixing. This method can produce a reliable mixing coefficient even with relatively low-quality field data. Effects of river discharge variation and ice cover on dimensional and dimensionless transverse mixing coefficient were investigated in a fixed river reach. Bubble plumes and bubbly jets produced by injecting air-water mixtures via a nozzle, were studied in crossflows in a large laboratory channel. Their general behaviors, mainly trajectories, were first photographically studied. Air and water discharges at the nozzle and the strength of crossflows were found to have significant impacts on the general behaviors. Proposed models could well simulate the trajectories of both gas-phase plumes and liquid-phase jets in crossflows. Detailed measurements on bubble properties in bubble plumes and bubbly jets in a crossflow were then conducted with a fiber-optic probe. Distributions of gas void fractions, bubble frequency, bubble velocity, bubble diameter and specific interfacial area were obtained at different crosssections. Centerline properties and spreading rates of bubble plumes were investigated. Relation of bubble slip velocity versus bubble diameter for bubbly jets in crossflow was obtained, and compared with those for single isolated bubbles and bubbly jets in stagnant water.
Language
English
DOI
doi:10.7939/R38D1V
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. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. 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.
Citation for previous publication
[1] Zhang, W.M., Rajaratnam, N, and Zhu, D.Z. (2011). “Transport with Jets and Plumes of Chemicals in the Environment”, Encyclopedia of Sustainability Science and Technology, Robert A. Meyers (ed.), DOI 10.1007/978-1-4419-0851-3, Springer, 25p.[2] Zhang, W.M., and Zhu, D.Z.(2011). “Near-field mixing downstream of a multiport diffuser in a shallow river.” J. Environ. Eng., ASCE, 137(4), 230-240.[3] Zhang, W.M., and Zhu, D.Z. (2011). “Transverse mixing in an unregulated natural river.” J. Hydraul. Eng., ASCE, 137(11), 1426-1440.[4] Zhang, W.M., and Zhu, D.Z. (2012). “Measurements of bubble plumes and bubbly jets in a crossflow.” J. Fluid Mech., submitted.[5] Zhang, W.M., and Zhu, D.Z. (2012). “Trajectories of bubble plumes and bubbly jets in crossflows.” Int. J. Multiphase Flow, to be submitted.

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