Velocity Field under Plunging Waves

Okayasu, Akio; Shibayama, Tomoya; Mimura, Naoya

doi:10.1061/9780872626003.050

Cited by 21 publications

(24 citation statements)

References 7 publications

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“…[3] On the basis of experimental measurements by a laser Doppler velocimeter (LDV) [e.g., Nadaoka et al, 1989;Okayasu et al, 1986;Kirby, 1995, 1996] and particle imaging velocimetry (PIV) [e.g., Chang and Liu, 1999;Melville et al, 2002], mean velocities and turbulence statistics have been described over a cross-shore vertical plane in breaking waves. By observing the motions of bubbles entrained by breaking waves, Nadaoka et al [1989] found that three-dimensional organized vortex structures, involving the so-called obliquely descending eddy, trap bubbles behind primary roller vortices.…”

Section: Introductionmentioning

confidence: 99%

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Watanabe

Mori

2008

J. Geophys. Res.

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[1] When ocean waves reach a surf zone, jets projecting from the breakers splash sequentially, producing horizontal roller vortices beneath the jets and longitudinal counterrotating vortices behind the rollers; these vortices organize into three-dimensional structures that evolve into a turbulent bore with wave propagation. This disrupts any uniform temperature distributions on the surface, creating heterogeneous patterns of surface temperatures. In this study, we extracted surface temperature distributions from infrared measurements in small-and large-scale wave flumes, then used those data to study the renewed surfaces created by subsurface vortices beneath spilling and plunging breakers. In our large-scale experiments, temporal and spatial scales of surface renewal and surface recovery were consistent with earlier work; however, in our small-scale experiments, the spatial scales showed significant deviations from earlier in situ observations. These inconsistencies may be attributed to scale effects for subsurface vortices, and we show that the Froude number (Fr) can be used to characterize the initial formation of longitudinal counterrotating vortices. Further, for turbulent flows fully developed by wave breaking in a bore region, the frequency of surface renewal correlates exponentially with Reynolds number (Re). The computed vorticity on the breaking wave surface exhibits local patterns which correlate strongly with the gravity induced counterrotating vortices, which in turn renew the rear-facing surface of the breaking waves. In contrast the turbulent bore which precedes the wave crest rapidly disturbs and renews the surface in front of the crest. These two different mechanisms for surface renewal, during the nearshore breaking process, lead to modulations in the surface temperature distribution and changes in thermal diffusivity during the propagation of the breaking wave.Citation: Watanabe, Y., and N. Mori (2008), Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves,

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Section: Introductionmentioning

confidence: 99%

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Watanabe

Mori

2008

J. Geophys. Res.

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“…Basco and Yamashita, 1986;and Okayasu et al, 1986). Therefore, the regression analysis between measured U m (at the breaking point) versus each possible formula of U w is used to determine the best-fit value Table 3.…”

Section: Mean Velocity Due To Wave Motionmentioning

confidence: 99%

“…However, Sato et al (1988) suggested using k 12 = 5.6 on the basis of the best fit with the measured undertows of Okayasu et al (1986) and Shimada (1982). Substituting Eq.…”

Section: Mean Velocity Due To Surface Rollermentioning

confidence: 99%

Simple Model for Undertow Profile

Rattanapitikon

Shibayama

2000

Coastal Engineering Journal

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Based on a re-analysis of the existing undertow models and the experimental results, a proper explicit model is proposed for computing undertow profile inside the surf zone. The model has been derived by using the eddy viscosity approach. The model is examined using published laboratory data from six sources covering small-scale and large-scale experiments, i.e. the experiments of Nadaoka et al. (1982), Hansen and Svendsen (1984), Okayasu et al. (1988), Cox et al. (1994), CRIEPI (Kajima et al., 1983) and SUPERTANK (Kraus and Smith , 1994). The present undertow model is considerably simpler than most of existing models. Although the model is simple, it shows good agreement with the experimental results above the bottom boundary layer. The calculation is so simple that the undertow profile can be calculated by using a pocket calculator. . Downloaded from www.worldscientific.com by MONASH UNIVERSITY on 08/26/15. For personal use only.

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“…Undertow models including the surface roller contribution were also developed by Stive and Wind [1986], Okayasu et al [1986], de Vriend and Stive [1987], Deigaard et al [1991], Smith et al [1992], Cox and Kobayashi [1998], Kuriyama and Nakatsukasa [2000] and others, while Dally and Dean [1984], Haines and Sallenger, Jr. [1994] and Masselink and Black [1995] formulated undertow models without the surface roller. The surface roller models were further developed by Nairn et al [1990], Okayasu et al [1990], Stive and de Vriend [1994], Dally and Brown [1995] and Renier and Battjes [1997], who modeled the evolution of a surface roller including the consideration of energy balance for waves and rollers.…”

Section: Introductionmentioning

confidence: 99%

A One-Dimensional Parametric Model for Undertow and Longshore Current Velocities on Barred Beaches

Kuriyama

2010

Coastal Engineering Journal

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A one-dimensional parametric model for undertow and longshore current velocities assuming a triangular velocity distribution in a surface roller was developed. This model as well as a parametric model with the assumption of a uniform velocity distribution in a roller was compared with field data obtained on barred beaches at Hasaki in Japan and at Duck in the USA. The comparisons showed that the present model predicted the velocity fields at the two sites reasonably well, and the prediction accuracy of the present model is slightly better than that of the other model. However, the present model underpredicted the undertow velocities on the trough regions, and overestimated the longshore current velocities near the shorelines.

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Velocity Field under Plunging Waves

Cited by 21 publications

References 7 publications

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Simple Model for Undertow Profile

A One-Dimensional Parametric Model for Undertow and Longshore Current Velocities on Barred Beaches

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