Laboratory study of the cross-shore flow structure in the surf and swash zones

Sou, In Mei; Yeh, Harry

doi:10.1029/2010jc006700

Cited by 21 publications

(35 citation statements)

References 27 publications

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“…Moreover, the peak uprush and backwash s xz magnitudes result in 80.8 N m -2 and 12.7 N m -2 , which compare to 77.8 N m -2 and 16.9 N m -2 for the impermeable case. Sou and Yeh [2011] investigated the ensemble-averaged vorticity field under plunging breakers in the surf and swash zones using PIV measurements. Their study validated the vorticity as an effective property to evaluate mechanisms that result from the combined action of pressure gradients, body forces at the water surface, and drag forces at the water-bed interface.…”

Section: 1002/2015jc010806mentioning

confidence: 99%

“…However, there are sub regions of alternating CCW and CW x near the surface indicating divergence/convergence patterns. Sou and Yeh [2011] also described advected CCW x at the surface inside the swash zone during the uprush phase which was related to wave-swash interactions in the inner surf zone. Here in the absence of wave-swash interactions, it is shown that local mechanisms are able to generate similar divergence/convergence patterns.…”

Section: Boundary Layer Growth Across the Swash Zonementioning

confidence: 99%

“…Previous studies have investigated the mean and turbulent flow field during the different phases of an individual swash cycle under natural [Puleo et al, 2000;Butt et al, 2004;Aagaard and Hughes, 2006;Raubenheimer et al, 2004;Blenkinsopp et al, 2011;Puleo et al, 2014b;Lanckriet et al, 2014] and laboratory [Cowen et al, 2003;Barnes et al, 2009;O'Donoghue et al, 2010;Sou et al, 2010;Sou and Yeh, 2011;Kikkert et al, 2012Kikkert et al, , 2013 conditions. Moreover, recent numerical studies [e.g., Brocchini and Baldock, 2008;Bakhtyar et al, 2009;Zhu and Dodd, 2013;Torres-Freyermuth et al, 2013] have provided additional information on the dynamics in this region, as they allow improved understanding of temporal and spatial variability of flow properties under different boundary/forcing conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Injection of bore related turbulence contributes to the cross-shore advection of particles into the swash zone that, together with the local mobilization, are effective in transporting sediment during swash cycle initiation [Butt and Russell, 1999;Puleo et al, 2000;Petti and Longo, 2001;Jackson et al, 2004;Masselink et al, 2005;Aagaard and Hughes, 2006]. During the remainder of the decelerating uprush motion, the turbulence decays similar to grid turbulence [Cowen et al, 2003;Sou and Yeh, 2011;Lanckriet and Puleo, 2013] and more homogeneously [Zhang and Liu, 2008] as the flow reaches the maximum inundation limit toward land (e.g., run up distance). Hence, sediment particles are more likely to settle during the flow reversal phase.…”

Section: Introductionmentioning

confidence: 99%

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On the role of infiltration and exfiltration in swash zone boundary layer dynamics

et al. 2015

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Boundary layer dynamics are investigated using a 2‐D numerical model that solves the Volume‐Averaged Reynolds‐Averaged Navier‐Stokes equations, with a VOF‐tracking scheme and a k ‐ ϵ turbulence closure. The model is validated with highly resolved data of dam break driven swash flows over gravel impermeable and permeable beds. The spatial gradients of the velocity, bed shear stress, and turbulence intensity terms are investigated with reference to bottom boundary layer (BL) dynamics. Numerical results show that the mean vorticity responds to flow divergence/convergence at the surface that result from accelerating/decelerating portions of the flow, bed shear stress, and sinking/injection of turbulence due to infiltration/exfiltration. Hence, the zero up‐crossing of the vorticity is employed as a proxy of the BL thickness inside the shallow swash zone flows. During the uprush phase, the BL develops almost instantaneously with bore arrival and fluctuates below the surface due to flow instabilities and related horizontal straining. In contrast, during the backwash phase, the BL grows quasi‐linearly with less influence of surface‐induced forces. However, the infiltration produces a reduction of the maximum excursion and duration of the swash event. These effects have important implications for the BL development. The numerical results suggest that the BL growth rate deviates rapidly from a quasi‐linear trend if the infiltration is dominant during the initial backwash phase and the flat plate boundary layer theory may no longer be applicable under these conditions.

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Section: 1002/2015jc010806mentioning

confidence: 99%

Section: Boundary Layer Growth Across the Swash Zonementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

et al. 2015

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“…There have also been many experimental attempts to visualise coherent vorticity structures in boundary layers or in rotating flows, but only a few in the bulk of fairly homogeneous isotropic flows (Dernoncourt et al 1998). Sou and Yeh (2011) employed particle image velocimetry to investigate the fundamental characteristics of the flow structure in the vertical cross-shore plane as the wave evolves from the outer surf zone to the swash zone. They suggested that vorticity generated near the bed has a simple relation to the pressure gradient for boundary layer flows.…”

Section: R Mukaromentioning

confidence: 99%

Vorticity filaments beneath regular turbulent flow

Mukaro

2017

J. S. Afr. Inst. Civ. Eng.

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Two-dimensional vorticity flow fields created in the wake of a plunging breaker were investigated for regular turbulent flow at a Reynolds number of 30 000. Velocity flow fields obtained from an earlier study that had employed digital particle image velocimetry, were analysed to determine vorticity shedding patterns and the interactions between the vorticity filaments as flow progressed. Central difference approximations were applied to the velocity fields to determine vorticity at each point in the field. Most of the strong instantaneous vorticity observed in the flow field was in the form of filaments. A hierarchy of filaments of different lengths were observed, with the longest being as long as the height of the wave used. During the early phases of the flow, instantaneous vorticity tended to organise into thin filaments of counter-rotating pairs. Eventually, the co-rotating vorticity filaments coalesced and ultimately merged in the turbulent flow as flow progressed, while counter-rotating vorticity filaments were cancelled by viscous dissipation. The results suggested that filaments travel more slowly than the wave velocity and drifted towards the bed as they became elongated, and the number of filaments remaining in the flow were observed to decrease as flow progressed. Whereas phase-resolved instantaneous vorticity results showed pairs of counter-rotating vorticity filaments near the crest, the phase-averaged vorticity description of flow fields showed a dominant primary positive vorticity filament around the shear boundary layer.

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Modeling swash‐zone hydrodynamics and shear stresses on planar slopes using Reynolds‐Averaged Navier–Stokes equations

2013

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.[1] A numerical model solving the Reynolds-Averaged Navier-Stokes equations, with a volume of fluid-tracking scheme and turbulence closure, is employed for estimating hydrodynamics in the swash zone. Model results for run-up distance, water depth, and near-bed velocity are highly correlated (r 2 > 0.97) with ensemble-averaged dam-break-driven swash data. Moreover, modeled bed shear stresses are within 20% of estimates derived from measured velocity profiles. Dam-break-driven swash simulations are conducted to determine the effect of foreshore characteristics (bed roughness and foreshore slope) on bore-induced swash-zone hydrodynamics and bed shear stresses. Numerical results revealed that the boundary layer vanishes during flow reversal, grows during the backwash, and becomes depth limited at the end of the swash cycle. In general, the uprush experiences larger shear stresses but for a shorter duration than the backwash. Some variability in this pattern is observed depending on the bed roughness, foreshore slope, and cross-slope location in the swash zone, implying that large spatial gradients in shear stresses can occur on the foreshore. The mean tangential force per unit area supplied to the bed is offshore directed for the simulated cases, with the exception of the mild-slope (1:25) cases, owing to the skewed nature of swash flows. The temporal evolution of the momentum balance inside the swash zone shows an important contribution to the total force from turbulence and advection at the early/final stage of the swash cycle, whereas the local acceleration does not appear to be a significant contribution.Citation: Torres-Freyermuth, A., J. A. Puleo, and D. Pokrajac (2013), Modeling swash-zone hydrodynamics and shear stresses on planar slopes using Reynolds-Averaged Navier-Stokes equations,

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Laboratory study of the cross-shore flow structure in the surf and swash zones

Cited by 21 publications

References 27 publications

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

Vorticity filaments beneath regular turbulent flow

Modeling swash‐zone hydrodynamics and shear stresses on planar slopes using Reynolds‐Averaged Navier–Stokes equations

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