Video DCIV measurements of mass and momentum fluxes and kinetic energies in laboratory waves breaking over a bar

Govender, K.; Michallet, Hervé; Alport, M. J.; Pillay, Ursula Monica.; Mocke, G.P.; Mory, Mathieu

doi:10.1016/j.coastaleng.2009.04.002

Cited by 11 publications

(7 citation statements)

References 25 publications

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“…From detailed PIV measurements of the velocities beneath plunging breaking waves (Govender et al 2002), it appears that this breakdown within the surfzone of the balance between pressure gradients and radiation stress gradients derived from linear wave theory arises from inaccuracies in the theoretical description of the velocity field within breaking waves. Linear wave theory and other nonbreaking wave theories (e.g., cnoidal) assume that PE and KE are equal (Dean and Dalrymple 1991;Dean and Bender 2006;Svendsen 2006).…”

Section: Discussionmentioning

confidence: 99%

“…From the experimental findings of Stive and Wind (1982) and Govender et al (2002Govender et al ( , 2009, as well as the three-dimensional finescale numerical simulations of Torres-Freyermuth et al (2007), it appears that the largest source of uncertainty in the evaluation of S xx for surfzone waves arises when evaluating ru 2 , specifically the contribution of velocities in the crest of breaking waves that is neglected in Eq. (4).…”

Section: B Radiation Stressesmentioning

confidence: 99%

“…Detailed particle image velocimetry (PIV) measurements of plunging waves (Govender et al 2002) have shown much larger velocities in the crest region relative to nonbreaking waves. In the surfzone, this can locally result in KE .…”

Section: Wave-roller Theorymentioning

confidence: 99%

“…In particular, we assess the ability of linear wave theory-derived radiation stress gradients approximated from observations to reproduce the observed setup and setdown responses. We also examine the contribution of a wave roller to the radiation stress (Svendsen 1984a;Reniers and Battjes 1997;Apotsos et al 2007) as a means of including the high onshore directed surface velocities observed in the crests of breaking waves and associated turbulent bores (e.g., Govender et al 2002). While this study specifically focuses on a representative fringing reef, our results are also relevant to understanding the mechanisms of wave setup generation by wave breaking on steep slopes more generally.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Wave Setup over a Steeply Sloping Fringing Reef

Buckley

Lowe

Hansen

et al. 2015

Journal of Physical Oceanography

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High-resolution observations from a 55-m-long wave flume were used to investigate the dynamics of wave setup over a steeply sloping reef profile with a bathymetry representative of many fringing coral reefs. The 16 runs incorporating a wide range of offshore wave conditions and still water levels were conducted using a 1:36 scaled fringing reef, with a 1:5 slope reef leading to a wide and shallow reef flat. Wave setdown and setup observations measured at 17 locations across the fringing reef were compared with a theoretical balance between the local cross-shore pressure and wave radiation stress gradients. This study found that when radiation stress gradients were calculated from observations of the radiation stress derived from linear wave theory, both wave setdown and setup were underpredicted for the majority of wave and water level conditions tested. These underpredictions were most pronounced for cases with larger wave heights and lower still water levels (i.e., cases with the greatest setdown and setup). Inaccuracies in the predicted setdown and setup were improved by including a wave-roller model, which provides a correction to the kinetic energy predicted by linear wave theory for breaking waves and produces a spatial delay in the wave forcing that was consistent with the observations.

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Section: Discussionmentioning

confidence: 99%

Section: B Radiation Stressesmentioning

confidence: 99%

Section: Wave-roller Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of Wave Setup over a Steeply Sloping Fringing Reef

Buckley

Lowe

Hansen

et al. 2015

Journal of Physical Oceanography

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“…On the other hand, observations of waves and hydrodynamics on barred beaches also have been collected over the years on the small‐scale laboratory experiments [e.g., Smith and Kraus , 1991; Cox and Kobayashi , 1998; Haller et al , 2002; Blenkinsopp and Chaplin , 2008; Govender et al , 2009] or in the field [e.g, Roelvink and Stive , 1989; Haines and Sallenger , 1994; Thornton et al , 1996; Elgar et al , 1997; Gallagher et al , 1998; Aagaard et al , 1998; Garcez Faria et al , 2000; Kuriyama , 2002; Marino‐Tapia et al , 2007a, 2007b]. Despite a number of research of hydrodynamics over a barred beach, turbulence observation is still rare due to the complex flow field caused by a barred beach, along with the difficulties mentioned previously.…”

Section: Introductionmentioning

confidence: 99%

Large‐scale laboratory observations of wave breaking turbulence over an evolving beach

Yoon

Cox

2010

J. Geophys. Res.

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[1] Wave breaking turbulence over an evolving beach was observed in a large-scale laboratory flume, as part of the CROss-Shore Sediment Transport EXperiment (CROSSTEX). The data set included comprehensive measurements of water surface elevation, fluid velocity, and morphology for irregular waves under erosive and accretive wave conditions. For the both conditions, the beach reached a quasi-equilibrium state, defined as when the bar shape was stable. Wave breaking characteristics, such as wave heights, average rate of energy dissipation by bores, and surf similarity parameter, were investigated in response to morphodynamics of the bar. Turbulent kinetic energy (TKE) was estimated using the method by Shaw and Trowbridge (2001). As the beach evolved, a less amount of TKE was observed at the trough for the erosive case, while more TKE was observed at the trough for the accretive case. It was also found that the temporal variation of the time-averaged TKE were closely associated with the average rate of energy dissipation by bores. Comparing with the bar trough, the vertical distribution of nondimensionalized time-averaged TKE and turbulence dissipation rate at the bar crest showed a large increase near the bottom, probably due to a strong cross-shore RMS velocity. Finally, in the quasi-equilibrium state, time-averaged TKE, and turbulence dissipation rate at the bar trough were smaller than those inside the surf zone. Inside the surf zone, significant turbulence intensities were observed due to a second breaking on a shallow water depth.

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