Structure and modeling of surf zone turbulence due to wave breaking

Mocke, G.P.

doi:10.1029/2000jc900163

Cited by 27 publications

(33 citation statements)

References 45 publications

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“…As discussed by Mocke [2001], a local equilibrium between dissipation and diffusion of TKE is associated with an exponential decay in the rate of dissipation in the form…”

Section: Resultsmentioning

confidence: 99%

“…This is certainly the case for positions above the approximate trough level. Through an examination of the cross-shore distribution of depth averaged turbulent kinetic energy in a number of plane slope experiments, Mocke [2001] speculates that the transition region for roller development extends to approximately 75% of the break point water depth. Both, stations 1 and 2, fall in this region.…”

Section: Resultsmentioning

confidence: 99%

“…[20] A modeling exercise [Mocke, 2001] based on the same experimental configuration indicates that the intensity of the boundary layer turbulence is very much smaller than that due to wave breaking. Thus the surf zone turbulence arises primarily from the transfer of energy due to wave breaking and it is reasonable to consider that the rate of production of turbulent kinetic energy should be of a similar magnitude.…”

Section: Resultsmentioning

confidence: 99%

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Dissipation of isotropic turbulence and length‐scale measurements through the wave roller in laboratory spilling waves

Govender

Mocke²,

Alport

2004

J. Geophys. Res.

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[1] The measurement of turbulence dissipation rates and length scales associated with three-dimensional isotropic structures under spilling waves breaking in a laboratory surf zone is presented. Dissipation rates were estimated from the spectral characteristics of the turbulence velocities in the inertial subrange, and length scales were estimated using measurements of the turbulent kinetic energy and dissipation rate. The spatial velocity flow fields for the above analysis were measured using digital correlation image velocimetry. A unique set of measurements that spans the entire water column, including the aerated portion near the crest of the wave, is presented. Dissipation rates were found to reach a maximum above the effective trough level, with over 80% of the depth integrated dissipation occurring in this upper zone. The total depth integrated turbulence dissipation rate is found to be up to an order of magnitude smaller than the local rate of wave energy dissipation due to breaking, the primary turbulence production source. The length scale is found to increase in magnitude below the surface, consistent with the idea that turbulence production occurs above the trough level in the vicinity of the wave roller and is transported downward toward the bed.INDEX TERMS: 4546 Oceanography: Physical: Nearshore processes; 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes; 4558 Oceanography: Physical: Sediment transport; KEYWORDS: digital correlation image velocimetry, dissipation rates, length scales, turbulent kinetic energy, wave breaking, surf zone Citation: Govender, K., G. P. Mocke, and M. J. Alport (2004), Dissipation of isotropic turbulence and length-scale measurements through the wave roller in laboratory spilling waves,

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“…As discussed by Mocke [2001], a local equilibrium between dissipation and diffusion of TKE is associated with an exponential decay in the rate of dissipation in the form…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Dissipation of isotropic turbulence and length‐scale measurements through the wave roller in laboratory spilling waves

Govender

Mocke²,

Alport

2004

J. Geophys. Res.

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“…The surf zone is generally two to three wave heights deep, implying that breaking-wave-induced turbulence should be able to penetrate all the way to the sea bed. Indeed, the potential of breaking wave turbulence to entrain sediment has been observed in the laboratory (Nadaoka et al 1988;Okayasu et al 2002) and suggested from field observations (e.g., Voulgaris and Collins 2000;Aagaard and Hughes 2010) and numerical models (Mocke 2001). Many models of sediment transport, however, relate the entrainment of sediment from the sea bed to bed-generated turbulence.…”

Section: Introductionmentioning

confidence: 99%

Observations of Turbulence within a Natural Surf Zone

Ruessink

2010

Journal of Physical Oceanography

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Here, the Reynolds stresses hu9w9i and hy9w9i, where u9, y9, and w9 are the cross-shore, alongshore, and vertical turbulence velocities, respectively, and the angle brackets represent time averaging, are used to diagnose turbulence dynamics beneath natural breaking surf-zone waves. The data were collected at Truc Vert Beach, France, during a 12-day period in 1-3-m water depth with strong cross-shore and alongshore currents under high-energy wave conditions (offshore significant wave heights ranged between 2 and 8 m). The hu9w9i term is predominantly negative, increases with the ratio of wave height H s to water depth h (;degree of wave breaking), and decreases in magnitude toward the bed. This supports the view that the cross-shore shear stress is due to breaking-induced vortices that transport high-speed cross-shore flow downward and disintegrate close to the bed. The occasional positive sign of hu9w9i within the lower 15%-20% of the water column indicates that sometimes surface-generated turbulence is overwhelmed by bed-generated turbulence, but the conditions when this happens are not clear from the data. The term hy9w9i is persistently of opposite sign to the alongshore mean current and decreases with height above the seabed, implying that hy9w9i is due to bottom boundary layer processes rather than surface-generated turbulence. The bottom drag coefficient amounted to 1.6 3 10 23 , similar to earlier observations. As in other high-Reynolds-number geophysical flows, time series of u9w9 and y9w9 comprise intermittently large, short-duration (here, ;1 s) stress events that in the data contribute considerably to the net stress in only 3%-15% of the time. The data further show that the turbulent kinetic energy is depth uniform and increases with H s /h. The depth-averaged Froudescaled turbulent kinetic energy beneath surf-zone bores is 0.025, a factor of 2 to 3 less than observed beneath regular laboratory waves.

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“…For example, it is shown in [11,12] that surging breaker and field of turbulence velocities have dominating influence on processes in coastal zone such as wave damping, flows of mass and impulse, currents, and sediment transport. On small water, breakers interact with seabed plants and sediments.…”

Section: Introductionmentioning

confidence: 99%