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

A, Dominic A. van der; Zanden, Joep van der; O’Donoghue, Thomas; Hurther, David; Caceres, Ivàn; McLelland, Stuart J.; Ribberink, Jan S.

doi:10.1002/2016jc012072

Cited by 41 publications

(37 citation statements)

References 49 publications

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“…Our results demonstrate the applicability of the plane wake and inner boundary layer assumptions for both spilling and plunging breakers. They are consistent with measurements in the large‐scale wave flume (Vander et al, ), in which the vertical velocity fluctuations

\overset{w^{' 2}}{true}

is restricted near the bed, resulting in more anisotropic turbulent eddies. A thicker boundary layer, in comparison to the turbulent boundary layer obtained in equation , is deduced.…”

Section: Turbulence Statisticssupporting

confidence: 90%

“…This is confirmed with the findings in Wilson et al () and Rodriguez‐Abudo and Foster (), in which the presence and ejection of vortices from wave breaking can significantly change the WSS. Moreover, Vander et al () measured the cross‐shore variation of WSS across a fixed bar. The reversal of WSS was observed near the breaking region and splash point.…”

Section: Discussionmentioning

confidence: 99%

“…Zou et al (, ) further developed a generalized solution of WSS distribution incorporating the effects of bottom slope and wave breaking, accounting for bottom dissipation with coupled wave and boundary layer flow. Moreover, several laboratory studies (De Serio & Mossa, ; Rodriguez‐Abudo & Foster, ; Ting & Nelson, ; Vander et al, ) and field studies (Elgar et al, ; Wilson et al, ; Zou et al, ) have confirmed that the magnitude of WSS is measurable. However, the measured magnitude and vertical distribution of WSS vary significantly in previous studies.…”

Section: Introductionmentioning

confidence: 91%

“…Below this depth,

\overset{\overset{u}{true} \overset{w}{true}}{true}

values again drop to zero due to the very small vertical wave component near the bottom boundary. Of note, the magnitude of WSS can be significantly greater than that of TSS, implying that WSS could dominate the vertical momentum flux (De Serio & Mossa, , ; Vander et al, ).…”

Section: Turbulent Shear Stress and Wave Shear Stressmentioning

confidence: 99%

“…However, the measured magnitude and vertical distribution of WSS vary significantly in previous studies. Differing studies found that the time‐averaged magnitude of WSS is greater than that of TSS (De Serio & Mossa, ; Vander et al, ) or the same order as TSS (Rodriguez‐Abudo & Foster, ), while the instantaneous WSS is mostly less than TSS (Ting & Nelson, ). Furthermore, some WSS measurements in water columns are inconsistent with the theory of Zou et al ().…”

Section: Introductionmentioning

confidence: 99%

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Laboratory Observation of Turbulence and Wave Shear Stresses Under Large Scale Breaking Waves Over a Mild Slope

Hsu

Huang

et al. 2019

JGR Oceans

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Laboratory measurements of turbulent flow and shear stresses in a surf zone under monochromatic breaking waves in a large‐scale wave flume are presented. Waves with various surf similarity parameters were generated to break at nearly identical water depths over a 1/100 mild slope. Free surface elevations were measured along the plane beach. Velocities in a water column located at the breaking region were measured by acoustic Doppler velocimeters. Results from wave shoaling coefficient, breaking index, and images are inconsistent with the breaker type categorizations from the surf similarity parameter. This suggests that a modification of the surf similarity parameter for very mild slopes may be necessary. For the plunging breakers, the ensemble‐averaged results indicate that intense turbulence kinetic energy was initially generated by large eddies at the surface then transported to the bottom frequently. The instantaneous results demonstrate that the intermittency of turbulence kinetic energy near the bed was caused by large eddies generated by wave overturning and relatively smaller obliquely descending eddies. Moreover, the magnitude of the wave shear stress (WSS) is one order of magnitude larger than that of the turbulent shear stress, indicating that the effects of the bottom slope, wave breaking, and bed friction are significant in the surf zone. The sign of the time‐averaged WSS switched between positive and negative, depending on the occurrences of phase lag and phase lead of the vertical coherent velocity. It suggests that a change may be required in Zou et al.'s (2006, https://doi.org/10.1029/2005JC003300) theory on the formulation of wave‐breaking induced WSS.

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\overset{w^{' 2}}{true}

is restricted near the bed, resulting in more anisotropic turbulent eddies. A thicker boundary layer, in comparison to the turbulent boundary layer obtained in equation , is deduced.…”

Section: Turbulence Statisticssupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

“…Below this depth,

\overset{\overset{u}{true} \overset{w}{true}}{true}

Section: Turbulent Shear Stress and Wave Shear Stressmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Laboratory Observation of Turbulence and Wave Shear Stresses Under Large Scale Breaking Waves Over a Mild Slope

Hsu

Huang

et al. 2019

JGR Oceans

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

Zanden

Caceres

et al. 2018

JGR Oceans

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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.

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