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Radially spreading surface flows Maclatchy, Michael Ray
Abstract
The present study investigated the radially spreading surface flow that is created when a vertical buoyant jet is discharged in shallow water and surfaces. Experiments were conducted for a series of vertical buoyant jets discharging into a shallow circular tank specially designed to simulate an infinite ambient water body so that downstream control effects were avoided. A range of flow rates and port diameters were utilized to determine the nature of the flow structure in the radially spreading surface region. Velocity profiles using an ADV, and temperature profiles using a thermistor array, were made throughout the radial flow region. The present study concentrated on the radial buoyant jet region of a vertical buoyant jet discharged in shallow water. In this region the surface flow rapidly entrained ambient fluid as it moved outward, and the rate at which fluid was entrained with distance was greater for the radially spreading flow than for the vertical jet itself. Both the bulk and minimum time-averaged dilutions increased linearly with radial distance. The upper layer depth increased in a parabolic fashion with radial distance, consistent with previous studies of mixing layers. The composite Froude number decreased gradually from its high initial values, but was never less than one through the entire radial extent in which measurements were made. Thus, for the range of conditions of this study the flow remained internally supercritical (on a time-averaged basis). This was also true for the stability Froude number, indicating that the radial flow was unstable and entrainment occurred throughout the radial extent investigated. No internal hydraulic jumps were found in the radially spreading surface flow in the present study. Significant entrainment into the radially spreading surface flow was found. The entrainment velocity was found to be proportional to the velocity difference between the upper and lower layers at larger radius where the radial flow had become established. The entrainment hypothesis of Morton, Taylor and Turner (1956) was consistent with the measured behaviour of the radially spreading surface flow in the present study.
Item Metadata
Title |
Radially spreading surface flows
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1999
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Description |
The present study investigated the radially spreading surface flow that is created when
a vertical buoyant jet is discharged in shallow water and surfaces. Experiments were
conducted for a series of vertical buoyant jets discharging into a shallow circular tank specially
designed to simulate an infinite ambient water body so that downstream control effects were
avoided. A range of flow rates and port diameters were utilized to determine the nature of the
flow structure in the radially spreading surface region. Velocity profiles using an ADV, and
temperature profiles using a thermistor array, were made throughout the radial flow region.
The present study concentrated on the radial buoyant jet region of a vertical buoyant
jet discharged in shallow water. In this region the surface flow rapidly entrained ambient fluid
as it moved outward, and the rate at which fluid was entrained with distance was greater for
the radially spreading flow than for the vertical jet itself. Both the bulk and minimum time-averaged
dilutions increased linearly with radial distance. The upper layer depth increased in a
parabolic fashion with radial distance, consistent with previous studies of mixing layers. The
composite Froude number decreased gradually from its high initial values, but was never less
than one through the entire radial extent in which measurements were made. Thus, for the
range of conditions of this study the flow remained internally supercritical (on a time-averaged
basis). This was also true for the stability Froude number, indicating that the radial flow was
unstable and entrainment occurred throughout the radial extent investigated.
No internal hydraulic jumps were found in the radially spreading surface flow in the
present study. Significant entrainment into the radially spreading surface flow was found. The
entrainment velocity was found to be proportional to the velocity difference between the upper
and lower layers at larger radius where the radial flow had become established. The
entrainment hypothesis of Morton, Taylor and Turner (1956) was consistent with the
measured behaviour of the radially spreading surface flow in the present study.
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Extent |
7090531 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-03
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0050143
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1999-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.