Oscillatory wave-induced boundary layer flow over a rippled bed
Oscillatory wave-induced boundary layer flow over a rippled bed
The aim of this project is to study the wave-induced flow above a rippled bed. Sea bed ripples do not have a major impact on the main flow pattern, but they strongly influence the structure of the boundary layer. Therefore they are of interest in coastal engineering as they are part of the sediment transport process and have influence on surface wave dissipation and flow friction in coastal areas.
By both numerical and experimental means, the flow characteristics were studied. A two-dimensional computer model solving this particular flow was developed and compared to other numerical and experimental data and the available theory. Experiments were conducted in a wave tank fitted with a rigid rippled bed, and flow visualizations were done using fluorescent dye filmed by a digital video camera. Different flow regimes were identified and were classified in terms of relevant parameters such as the ripple slope, the wave orbital amplitude to ripple wavelength ratio and the Taylor number. For a weak flow oscillation to ripple wavelength ratio, two-dimensional structures tend to develop in the form of recirculation cells. For a stronger flow oscillation and a medium to steep ripple slope, the flow separates giving rise to vortices ejected from the ripple crests every half-wave period. Three-dimensional instabilities also appear in two different forms. The most common form observed is a structure of "rings". The other form called brick-pattern is suspected to involve centrifugal instabilities and play a major role in the building of three-dimensional ripple shapes. A final summary of the flow characteristics was done, using the numerical and experimental results.
University of Southampton
Ourmieres, Yann
231d7e12-72d2-4650-ac2d-af9857d741f6
2003
Ourmieres, Yann
231d7e12-72d2-4650-ac2d-af9857d741f6
Ourmieres, Yann
(2003)
Oscillatory wave-induced boundary layer flow over a rippled bed.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The aim of this project is to study the wave-induced flow above a rippled bed. Sea bed ripples do not have a major impact on the main flow pattern, but they strongly influence the structure of the boundary layer. Therefore they are of interest in coastal engineering as they are part of the sediment transport process and have influence on surface wave dissipation and flow friction in coastal areas.
By both numerical and experimental means, the flow characteristics were studied. A two-dimensional computer model solving this particular flow was developed and compared to other numerical and experimental data and the available theory. Experiments were conducted in a wave tank fitted with a rigid rippled bed, and flow visualizations were done using fluorescent dye filmed by a digital video camera. Different flow regimes were identified and were classified in terms of relevant parameters such as the ripple slope, the wave orbital amplitude to ripple wavelength ratio and the Taylor number. For a weak flow oscillation to ripple wavelength ratio, two-dimensional structures tend to develop in the form of recirculation cells. For a stronger flow oscillation and a medium to steep ripple slope, the flow separates giving rise to vortices ejected from the ripple crests every half-wave period. Three-dimensional instabilities also appear in two different forms. The most common form observed is a structure of "rings". The other form called brick-pattern is suspected to involve centrifugal instabilities and play a major role in the building of three-dimensional ripple shapes. A final summary of the flow characteristics was done, using the numerical and experimental results.
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Published date: 2003
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Local EPrints ID: 465146
URI: http://eprints.soton.ac.uk/id/eprint/465146
PURE UUID: cd70849e-8141-4af7-9d09-747528c3e0a8
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Date deposited: 05 Jul 2022 00:25
Last modified: 16 Mar 2024 19:59
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Author:
Yann Ourmieres
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