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

Jose Carlos Pintado-Pati, Alec Torres-Freyermuth, Jack A. Puleo, Dubravka Pokrajac

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Abstract

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.
Original languageEnglish
Pages (from-to)6329-6350
Number of pages22
JournalJournal of Geophysical Research: Oceans
Volume120
Issue number9
Early online date19 Sep 2015
DOIs
Publication statusPublished - Sep 2015

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wave runup
infiltration
boundary layer
bottom stress
turbulence
vorticity
shear stress
benthic boundary layer
Navier-Stokes equations
plate boundary
gravel
dam
divergence

Keywords

  • swash zone
  • hydrodynamics
  • boundary layer

Cite this

On the role of infiltration and exfiltration in swash zone boundary layer dynamics. / Pintado-Pati, Jose Carlos; Torres-Freyermuth, Alec ; Puleo, Jack A. ; Pokrajac, Dubravka.

In: Journal of Geophysical Research: Oceans, Vol. 120, No. 9, 09.2015, p. 6329-6350.

Research output: Contribution to journalArticle

Pintado-Pati, Jose Carlos ; Torres-Freyermuth, Alec ; Puleo, Jack A. ; Pokrajac, Dubravka. / On the role of infiltration and exfiltration in swash zone boundary layer dynamics. In: Journal of Geophysical Research: Oceans. 2015 ; Vol. 120, No. 9. pp. 6329-6350.
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title = "On the role of infiltration and exfiltration in swash zone boundary layer dynamics",
abstract = "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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author = "Pintado-Pati, {Jose Carlos} and Alec Torres-Freyermuth and Puleo, {Jack A.} and Dubravka Pokrajac",
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N1 - Funded by Mexican National Council of Science and Technology (CoNACyT) . Grant Number: 490080 Fulbright-Garcia Robles grant Instituto de Ingeniería UNAM International Collaborative Research project University of Delaware DGAPA UNAM National Science Foundation . Grant Numbers: OCE-0845004 , OCE-1332703 University of Delaware UK Engineering and Physical Sciences Research Council ‘Flood MEMORY: Multi-Event Modelling Of Risk & recoverY’ . Grant Number: EP EP/K013513/1

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N2 - 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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