Refraction of Surface Gravity Waves by Shear Waves

Henderson, Stephen M.; Guza, R. T.; Elgar, Steve; Herbers, T. H. C.

doi:10.1175/jpo2890.1

Cited by 13 publications

(9 citation statements)

References 15 publications

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“…In the inner surf zone (F1–F3), the (m) continues to decrease following Snell's law, but the (obs) increase, possibly due to wave reflection that is not included in the model. Both the model and observed θ increase in the inner surf zone, as previously observed by Herbers et al [1999], possibly due to the eddy field randomly refracting sea swell waves [e.g., Henderson et al , 2006]. However, (obs) increases more rapidly than (m) closer to the shoreline, also potentially due to the lack of wave reflection in the model.…”

Section: Bulk Parameter Model‐data Comparisonssupporting

confidence: 74%

Modeling surf zone tracer plumes: 1. Waves, mean currents, and low‐frequency eddies

2011

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[1] A model that accurately simulates surf zone waves, mean currents, and low-frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion. In this paper, a wave-resolving time-dependent Boussinesq model is compared with waves and currents observed during five surf zone dye release experiments. In a companion paper, Clark et al. (2011) compare a coupled tracer model to the dye plume observations. The Boussinesq model uses observed bathymetry and incident random, directionally spread waves. For all five releases, the model generally reproduces the observed cross-shore evolution of significant wave height, mean wave angle, bulk directional spread, mean alongshore current, and the frequency-dependent sea surface elevation spectra and directional moments. The largest errors are near the shoreline where the bathymetry is most uncertain. The model also reproduces the observed cross-shore structure of rotational velocities in the infragravity (0.004 < f < 0.03 Hz) and very low frequency (VLF) (0.001 < f < 0.004 Hz) bands, although the modeled VLF energy is 2-3 times too large. Similar to the observations, the dominant contributions to the modeled eddy-induced momentum flux are in the VLF band. These eddies are elliptical near the shoreline and circular in the mid surf zone. The model-data agreement for sea swell waves, low-frequency eddies, and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion.

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Section: Bulk Parameter Model‐data Comparisonssupporting

confidence: 74%

Modeling surf zone tracer plumes: 1. Waves, mean currents, and low‐frequency eddies

2011

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“…Waves were normally incident and directionally spread, and the wave conditions seaward of the surfzone were nearly constant. At the array the significant wave height H sig varied with the tidally fluctuating water depth (Figure 3c), the directional spread [ Kuik et al , 1988] varied inversely with depth from 16° to 22° (possibly by wave current interaction [ Henderson et al , 2006]), the mean period was 8 s, and the hourly mean alongshore currents were weak (<0.08 m/s).…”

Section: Methodsmentioning

confidence: 99%

Vorticity generation by short‐crested wave breaking

Clark

Elgar

Raubenheimer

2012

Geophysical Research Letters

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Eddies and vortices associated with breaking waves rapidly disperse pollution, nutrients, and terrestrial material along the coast. Although theory and numerical models suggest that vorticity is generated near the ends of a breaking wave crest, this hypothesis has not been tested in the field. Here we report the first observations of wave‐generated vertical vorticity (e.g., horizontal eddies), and find that individual short‐crested breaking waves generate significant vorticity [O(0.01 s−1)] in the surfzone. Left‐ and right‐handed wave ends generate vorticity of opposite sign, consistent with theory. In contrast to theory, the observed vorticity also increases inside the breaking crest, possibly owing to onshore advection of vorticity generated at previous stages of breaking or from the shape of the breaking region. Short‐crested breaking transferred energy from incident waves to lower frequency rotational motions that are a primary mechanism for dispersion near the shoreline.

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“…Some relevant studies illustrating the effects of wave-current interaction in coastal and nearshore areas have considered the changes in wavenumber and phase speed of waves as they propagate over a spatially varying but depth-uniform and steady current, 1 the change in surface wave heights due to tidal currents, 2,3 wave-current instabilities leading to the onset of rip current cells, 4 and the refraction of waves due to shallow water vortical motions. 5,6 For the case of depth-uniform currents, wave-current interaction theory is generally well developed and comprehensive reviews can be found in Refs. 7-13. In practice, the vast majority of wave-current interaction analyses are done using the quasi-stationary current assumption, which considers the current field ͑and total water depths͒ to be stationary at time scales relevant to the wave propagation problem.…”

Section: Introductionmentioning

confidence: 99%

Waves on unsteady currents

Haller

Özkan-Haller

2007

Physics of Fluids

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Models for surface gravity wave propagation in the presence of currents often assume the current field to be quasi-stationary, which implies that the absolute wave frequency is time invariant. However, in the presence of unsteady currents or time-varying water depth, linear wave theory predicts a time variation of the absolute wave frequency ͑and wavenumber͒. Herein, observations of wave frequency modulations from a large-scale laboratory experiment are presented. In this case, the modulations are caused by both unsteady depths and unsteady currents due to the presence of low-frequency standing waves. These new observations allow a unique and detailed verification of the theoretical predictions regarding variations in the absolute wave frequency. In addition, analytic solutions for the variations in frequency and wave height induced by the unsteady medium are found through a perturbation analysis. These solutions clarify the dependency of the wave frequency/wave height modulations on the characteristics of the unsteady medium. We also find that analytic solutions for simplified basin configurations provide an order of magnitude estimate of the expected frequency modulation effect. Finally, the importance of this phenomenon in natural situations is discussed.

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Refraction of Surface Gravity Waves by Shear Waves

Cited by 13 publications

References 15 publications

Modeling surf zone tracer plumes: 1. Waves, mean currents, and low‐frequency eddies

Modeling surf zone tracer plumes: 1. Waves, mean currents, and low‐frequency eddies

Vorticity generation by short‐crested wave breaking

Waves on unsteady currents

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