Experimental study of bore-driven swash hydrodynamics on impermeable rough slopes

Kikkert, Gustaaf Adriaan; O’Donoghue, Thomas; Pokrajac, Dubravka; Dodd, Nicholas

doi:10.1016/j.coastaleng.2011.09.006

Cited by 78 publications

(138 citation statements)

References 24 publications

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“…This assumption has been commonly employed in field studies [e.g., Raubenheimer et al, 2004;Masselink et al, 2005], based on single point or coarse velocity measurements, leading to consistent estimates of bed shear stresses and friction coefficients. However, laboratory based studies of swash flows over fixed beds have concluded that the log law does not predict adequately the leading and trailing edges of the bore front [Barnes et al, 2009], and the near flow reversal phases [Cox et al, 2001;Archetti and Brocchini, 2002;O'Donoghue et al, 2010;Kikkert et al, 2012]. Thus, the suitability of this assumption under natural settings may be limited to certain flow conditions [Puleo et al, 2012[Puleo et al, , 2014a as confirmed by field measurements of near bed velocity profiles at a highresolution (100 Hz at 1 mm vertical spacing).…”

Section: Introductionmentioning

confidence: 97%

“…The data sets used for the model validation correspond to the laboratory experiments conducted by Kikkert et al [2012Kikkert et al [ , 2013 and hence only a general overview is here provided. The experimental setup consists of a wave flume facility with dimensions of 20 m long, 0.9 m high, and 0.45 m wide.…”

Section: Experimental Layoutmentioning

confidence: 99%

“…Cross-correlation particle image velocimetry (PIV) and laser induced fluorescence (LIF) techniques were used by Kikkert et al [2012Kikkert et al [ , 2013 in order to measure the vertical profile of the bed-parallel (u x ) and bedorthogonal (u x ) velocity and instantaneous water depths at 6 cross-shore locations. Ensemble-averaged quantities and turbulence measurements were obtained after repeating identical conditions over 50 tests for PIV/LIF measurements and 10 times for the shoreline motion LIF measurements.…”

Section: Experimental Layoutmentioning

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%

“…In this paper, experimental data sets, consisting of dam-break-driven flows over impermeable [Kikkert et al, 2012] and permeable [Kikkert et al, 2013] fixed beds, are used to validate a numerical model for its use inside the swash zone. We further investigate the effects of bed characteristics on swash zone boundary layer dynamics by quantifying the differences in the mean and turbulence flow fields.…”

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: Introductionmentioning

confidence: 97%

Section: Experimental Layoutmentioning

confidence: 99%

Section: Experimental Layoutmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

et al. 2015

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Large eddy simulation of dam‐break‐driven swash on a rough‐planar beach

Kim

Zhou

Hsu

et al. 2017

J. Geophys. Res. Oceans

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Turbulence characteristics in the swash zone are investigated using a 3‐D large eddy simulation model. The numerical model is implemented based on OpenFOAM which solves the filtered Navier‐Stokes equations for two immiscible fluids with a standard Smagorinsky subgrid‐scale closure. The numerical model is validated with laboratory data for swash flow driven by a dam‐break apparatus. The model results demonstrate that the main characteristics of turbulence in the swash zone are different from those in the surf zone, which are mainly induced by surface wave breaking. During uprush phase, bore‐generated turbulence has 2‐D turbulence characteristics because of limited water depth. Near‐bed‐generated turbulence is mainly observed during backwash. Turbulence production and turbulent dissipation rate estimated from the model results indicate an imbalance, possibly due to advection at swash front and large roughness used. Touching down of turbulent coherent structure (TCS) is observed during uprush, which drives intense bed shear stress. During the backwash, interaction between TCS and bed is less clear. However, finger‐like patterns in the spatial extent of bed shear stress and vertical components of vorticity are predicted during the backwash. The location of the strongest finger patterns in the vertical direction is collocated with that of maximum turbulence production. These finger patterns are likely caused by boundary layer instabilities injected vertically from the bed.

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A 2D hydrodynamic model for shallow water flows with significant infiltration losses

Cao

Liu

et al. 2020

Hydrological Processes

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Infiltration losses may be significant and warrant proper incorporation into mathematical models for river floods in arid and semi-arid areas, rainfall-induced surface runoffs in watersheds and swashes on beaches. Here, a depth-averaged twodimensional hydrodynamic model is presented for such processes based on the cellcentred finite volume method on unstructured meshes, with the full Green-Ampt equation evaluating the infiltration rate. A local time stepping strategy is employed along with thread parallelization with Open Multi-processing and high-performance computing to reduce model run time and therefore facilitate applications for largescale processes. The numerical solutions generally agree with the experimental and field-measured data for typical cases with significant infiltration losses. The case study shows that neglecting infiltration leads to an overestimated discharge hydrograph, which cannot be compensated by means of varied bed resistance as estimated by Manning roughness, and the infiltration parameters play disparate roles in modifying shallow flows compared with Manning roughness. In addition, infiltration affects bed shear stress, which in turn modifies the critical bed sediment size that could be initiated for incipient motion by the flow and therefore needs to be properly accounted for when sediment transport and morphological evolution are to be resolved. K E Y W O R D Shydrodynamic model, infiltration loss, river flood, surface runoff, swash

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Experimental study of bore-driven swash hydrodynamics on impermeable rough slopes

Cited by 78 publications

References 24 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

Large eddy simulation of dam‐break‐driven swash on a rough‐planar beach

A 2D hydrodynamic model for shallow water flows with significant infiltration losses

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