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Near-Bed Turbulent Kinetic Energy Budget Under a Large-Scale Plunging Breaking Wave Over a Fixed Bar

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

Authors

Joep van der Zanden

Dominic A. van der A

Iván Cáceres

David Hurther

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Dr Stuart McLelland S.J.McLelland@hull.ac.uk
Deputy Director of the Energy and Environment Institute

Jan S. Ribberink

Tom O'Donoghue



Abstract

Hydrodynamics under regular plunging breaking waves over a fixed breaker bar were studied in a large-scale wave flume. A previous paper reported on the outer flow hydrodynamics; the present paper focuses on the turbulence dynamics near the bed (up to 0.10 m from the bed). Velocities were measured with high spatial and temporal resolution using a two component laser Doppler anemometer. The results show that even at close distance from the bed (1 mm), the turbulent kinetic energy (TKE) increases by a factor five between the shoaling, and breaking regions because of invasion of wave breaking turbulence. The sign and phase behavior of the time-dependent Reynolds shear stresses at elevations up to approximately 0.02 m from the bed (roughly twice the elevation of the boundary layer overshoot) are mainly controlled by local bed-shear-generated turbulence, but at higher elevations Reynolds stresses are controlled by wave breaking turbulence. The measurements are subsequently analyzed to investigate the TKE budget at wave-averaged and intrawave time scales. Horizontal and vertical turbulence advection, production, and dissipation are the major terms. A two-dimensional wave-averaged circulation drives advection of wave breaking turbulence through the near-bed layer, resulting in a net downward influx in the bar trough region, followed by seaward advection along the bar's shoreward slope, and an upward outflux above the bar crest. The strongly nonuniform flow across the bar combined with the presence of anisotropic turbulence enhances turbulent production rates near the bed.

Citation

van der Zanden, J., van der A, D. A., Cáceres, I., Hurther, D., McLelland, S. J., Ribberink, J. S., & O'Donoghue, T. (2018). Near-Bed Turbulent Kinetic Energy Budget Under a Large-Scale Plunging Breaking Wave Over a Fixed Bar. Journal of Geophysical Research: Oceans, 123(2), 1429-1456. https://doi.org/10.1002/2017jc013411

Acceptance Date Jan 28, 2018
Online Publication Date Feb 24, 2018
Publication Date Feb 24, 2018
Deposit Date Feb 26, 2018
Publicly Available Date Feb 28, 2018
Journal Journal of Geophysical Research: Oceans
Print ISSN 2169-9291
Electronic ISSN 2169-9291
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 123
Issue 2
Pages 1429-1456
DOI https://doi.org/10.1002/2017jc013411
Keywords Breaking waves; Turbulence; Wave bottom boundary layer; Surf zone; Wave flume experiment; Breaker bar
Public URL https://hull-repository.worktribe.com/output/596697
Publisher URL http://onlinelibrary.wiley.com/doi/10.1002/2017JC013411/abstract
Copyright Statement © 2018. 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.

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https://creativecommons.org/licenses/by/4.0/

Copyright Statement
© 2018. 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.





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