Large-scale laboratory study of breaking wave hydrodynamics over a fixed bar

van der A., Dominic A.; van der Zanden, Joep; O'Donoghue, Tom; Hurther, David; Cáceres, Iván; McLelland, S. J.(Stuart J.); Ribberink, Jan S.

Department of Geography, Environment and Earth Sciences
Breaking waves; TKE; Fixed breaker bar; Wave flume experiment; Plunging wave; Turbulence
2017

Journal article


Rights
© 2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Abstract

A large-scale wave flume experiment has been carried out involving a T54 s regular wave with H50.85 m wave height plunging over a fixed barred beach profile. Velocity profiles were measured at 12 locations along the breaker bar using LDA and ADV. A strong undertow is generated reaching magnitudes of 0.8 m/s on the shoreward side of the breaker bar. A circulation pattern occurs between the breaking area and the inner surf zone. Time-averaged turbulent kinetic energy (TKE) is largest in the breaking area on the shoreward side of the bar where the plunging jet penetrates the water column. At this location, and on the bar crest, TKE generated at the water surface in the breaking process reaches the bottom boundary layer. In the breaking area, TKE does not reduce to zero within a wave cycle which leads to a high level of ‘‘residual’’ turbulence and therefore lower temporal variation in TKE compared to previous studies of breaking waves on plane beach slopes. It is argued that this residual turbulence results from the breaker bar-trough geometry, which enables larger length scales and time scales of breaking- generated vortices and which enhances turbulence production within the water column compared to plane beaches. Transport of TKE is dominated by the undertow-related flux, whereas the wave-related and turbulent fluxes are approximately an order of magnitude smaller. Turbulence production and dissipation are largest in the breaker zone and of similar magnitude, but in the shoaling zone and inner surf zone production is negligible and dissipation dominates.

Publisher
The University of Hull
Peer reviewed
Yes
Language
English
Extent
4 MB
Identifier
hull:15437

Journal

Journal title
Journal of geophysical research : oceans
Publication date
2017
Publisher
American Geophysical Union
DOI
10.1002/2016JC012072
ISSN (Print)
2169-9291
ISSN (Electronic)
2169-9291
Volume
122
Issue
4
Start page
3287
End page
3310
Notes

Copy of article first published in: Journal of geophysical research : oceans, 2017, v.122, issue 4

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