Analysis of surf zone turbulence

Svendsen, Ib A.

doi:10.1029/jc092ic05p05115

Cited by 209 publications

(174 citation statements)

References 11 publications

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“…Stive separated turbulent and wave motions by ensemble phase averaging which probably slightly overestimates the turbulence intensity because of irregularities unrelated to turbulence in paddle-generated waves [Svendsen, 1987]. This is consistent with u'/u', > 1 as observed for the Stive data (Figure 9a).…”

Section: Comparison To Laboratory Resultssupporting

confidence: 75%

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Observations of turbulence in the surf zone

George¹,

Flick²,

Guza³

1994

J. Geophys. Res.

138

108

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Turbulence generated by waves breaking on a natural beach is examined using hotfilm anemometer data. Turbulence intensity is estimated from dissipation rates determined from wavenumber spectra of short (1/8 s) hotfilm time series. The resulting Froude‐scaled turbulence intensities are relatively uniform between the seabed and the wave trough level and are similar in vertical structure but lower in magnitude than in existing laboratory studies. The magnitudes of the turbulence intensities observed in both the field and laboratory are consistent with an existing macroscopic model of bore dissipation in the surf zone. Scaling by this bore model relates turbulence intensities generated by monochromatic waves in small‐scale laboratory experiments to those generated by random waves in the natural surf zone.

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Section: Comparison To Laboratory Resultssupporting

confidence: 75%

“…The mean deviation (over the vertical) of u'/u', from 1.0 is about +.05, less than the scatter in the estimates themselves at a given vertical position. Turbulence intensities were also Froude scaled (i.e., normalized by (gh)l ', [Svendsen, 1987]) in Figure 7(c) for comparison with laboratory data in thQ following section.…”

mentioning

confidence: 99%

Observations of turbulence in the surf zone

George¹,

Flick²,

Guza³

1994

J. Geophys. Res.

138

108

View full text Add to dashboard Cite

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“…This length scale is about a fifth as large as those reported by Flick and George (1990) for surf zone flows 20 cm above a smooth sandy beach. It is also about twice as large as the elevation above the bottom of the sensing element of the flow probe, and is therefore consistent with order of magnitude expectations provided by turbulence theory (e.g., Svendsen 1987).…”

Section: Insupporting

confidence: 72%

Biological implications of surf‐zone flow complexity

Gaylord

2000

Limnology & Oceanography

100

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Wave action imposes potentially large hydrodynamic forces on intertidal plants and animals, and can act as a primary agent of disturbance. It has also been proposed that rapid water accelerations produced by breaking waves might constrain the sizes to which intertidal organisms can grow. However, despite the proven ecological importance of surf-zone flows, few actual measurements of forces imposed on plants or animals by waves in nature have been conducted. In this study, real-time wave forces acting on individuals of the rockweed Pelvetia compressa and a sea urchin Strongylocentrotus purpuratus are recorded in the field. These measured forces are compared with values predicted from theory using laboratory-determined shape factors (i.e., drag and added mass coefficients) and simultaneous flow measurements conducted adjacent to the deployed samples. Results demonstrate that models predicting large contributions of force due to water's acceleration are likely inaccurate, most probably because such models fail to account for the small spatial scales of surf-zone accelerations. This likely eliminates any capacity for intertidal hydrodynamic accelerational forces to limit size, contrary to previous conjectures. Data also suggest that wave-induced forces predicted from simple fluid dynamic expressions can, but sometimes do not, reflect accurately the forces applied. Together these findings imply that although traditional hydrodynamic theory may indeed provide a valuable tool for predicting forces imposed on immersed surf-zone organisms, such approaches must be used with caution. Finally, the field recordings suggest that sharp, transient forces arising from the impingement of waves directly on non-submerged organisms may in general impose the most severe loadings experienced by intertidal plants and animals, a possibility that to date has received little attention. The precise consequences of such brief forces depend on the level of flexibility or rigidity of an organism's construction.In intertidal regions of rocky shores, forces imposed by breaking waves may act as one of the dominant mechanisms determining species presence or abundance, plant and animal diversity, and community structure (Lewis 1964;1968;Dayton 1971;Connell 1978;Paine and Levin 1981;Sousa 1984Sousa , 1985Ricketts et al. 1985). However, despite their importance, wave exposure and the magnitudes of imposed hydrodynamic forces have proven difficult to estimate. Most studies that have attempted to evaluate consequences of breaking waves for intertidal organisms have relied on standard fluid-dynamic theory coupled with idealized flow scenarios that may or may not accurately describe effects of the complex and rapidly evolving water motions of the surf zone (e.g., Koehl 1977;1986;Denny et al. 1985;Denny 1987;1995;Carrington 1990; Denny and Gaines 1990;Dudgeon and Johnson 1992;Bell and Denny 1994;Gaylord et al. 1994; Denny and Gaylord 1996;Blanchette 1997). Thus the validity of models designed to predict the severity or 1 Present address: Dept. Ec...

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“…In the model of Peregrine and Svendsen [1978] the generated turbulence is considered to be spread downstream and toward the bottom as in a mixing layer. Using detailed flow visualization techniques and measurements, Nadaoka et al [1989] Svendsen [1987] recommends an ensemble-averaging separation method. This method cannot, however, be used Ibr random waves, where a ming-mean or frequency filter separation is invariably applied.…”

Section: Introductionmentioning

confidence: 99%

Structure and modeling of surf zone turbulence due to wave breaking

Mocke¹

2001

J. Geophys. Res.

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Abstract. The turbulence structure under breaking waves in the surf zone is investigated through reference to experimental measurements and turbulence closure modeling. This includes a unique set of recent turbulence measurements that have extended into the roller area through the application of digital particle image velocimetry. Measurements highlight the surface roller as the primary agent for turbulence production, from where it is transported downward principally because of turbulent diffusion. Reflecting the breaker transition process, turbulence intensities are largest some distance shoreward of the breaker point where the roller is fully developed. The temporal variation of turbulence at a fixed point below the wave trough level is generally found to be minimal, supporting the present use of a time-independent turbulence closure model. Production of turbulent kinetic energy in the two-equation (k-e) model is presumed to occur in the vicinity. of the surface roller, from where it is transported downward through the water column by diffusion. This production, which is estimated from the rate of energy dissipation in the wave roller, is the principal input parameter for the k-e model. Froude scaled turbulence measurements from laboratory and field experiments are found to be satisfactorily predicted within the limits of the developed surf zone, with improved methods of incorporating wave breaker transition zone effects leading to further model refinement. The turbulence closure model is further shown to be effective in predicting time mean suspended sediment concentration and undertow velocity profiles in the surf zone.

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Analysis of surf zone turbulence

Cited by 209 publications

References 11 publications

Observations of turbulence in the surf zone

Observations of turbulence in the surf zone

Biological implications of surf‐zone flow complexity

Structure and modeling of surf zone turbulence due to wave breaking

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