Low-frequency, many-minute-period horizontal surfzone eddies are an important mechanism for the dispersion of material, transporting larvae, pollutants, sediment, and swimmers both across and along the nearshore. Previous numerical, laboratory, and field observations on alongshore uniform bathymetry with no or roughly uniform mean background flows suggest that the low-frequency eddies may be the result of a two-dimensional inverse energy cascade that transfers energy from relatively small spatial-scale vorticity injected by depth limited breaking waves to larger and larger spatial scales. Here, using remotely sensed high-spatial resolution estimates of currents, those results are extended to surfzones with strong complex mean circulation patterns [flows O(1 m/s)] owing to nonuniform bathymetry. Similar to previous results, wavenumber spectra and second-order structure functions calculated from the observations are consistent with a two-dimensional inverse energy cascade. The size of the largest eddies is shown to depend on the surfzone width and the spatial scales of the mean currents. Third-order structure functions also are consistent with an inverse cascade for spatial scales greater than ∼50 m. At smaller scales, the third-order structure functions suggest a mixture of inverse and forward cascades.
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August 2023
Research Article|
August 30 2023
Observations of two-dimensional turbulence in the surfzone
Special Collection:
Recent Advances in Marine Hydrodynamics
Steve Elgar
;
Steve Elgar
a)
(Conceptualization, Data curation, Formal analysis, Funding acquisition, Project administration, Writing – original draft)
Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution
, 266 Woods Hole Rd., Woods Hole, Massachusetts 02543, USA
a)Author to whom correspondence should be addressed: elgar@whoi.edu
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Ciara Dooley
;
Ciara Dooley
(Data curation, Software, Writing – review & editing)
Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution
, 266 Woods Hole Rd., Woods Hole, Massachusetts 02543, USA
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Levi Gorrell
;
Levi Gorrell
(Software, Writing – review & editing)
Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution
, 266 Woods Hole Rd., Woods Hole, Massachusetts 02543, USA
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Britt Raubenheimer
Britt Raubenheimer
(Data curation, Funding acquisition, Writing – review & editing)
Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution
, 266 Woods Hole Rd., Woods Hole, Massachusetts 02543, USA
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a)Author to whom correspondence should be addressed: elgar@whoi.edu
Physics of Fluids 35, 085142 (2023)
Article history
Received:
May 21 2023
Accepted:
July 27 2023
Citation
Steve Elgar, Ciara Dooley, Levi Gorrell, Britt Raubenheimer; Observations of two-dimensional turbulence in the surfzone. Physics of Fluids 1 August 2023; 35 (8): 085142. https://doi.org/10.1063/5.0159170
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