Fluid–particle interaction and generation of coherent structures over permeable beds: an experimental analysis

Corvaro, Sara; Miozzi, Massimo; Postacchini, Matteo; Mancinelli, Alessandro; Brocchini, Maurizio

doi:10.1016/j.advwatres.2014.05.015

Cited by 16 publications

(16 citation statements)

References 22 publications

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“…Consistent with Corvaro et al [2014] observations (Figures 5a1-5c1), the numerical model predicts fluctuations (Figures 5b2-5c2) around the mean flow driven by local pressure gradients under such oscillatory flow conditions. These fluctuations are described in Corvaro et al [2014] as standing vortices that induce large scale modulations around the mean flow velocity while they propagate from one interstitial space to the next one in the local direction of the flow. This is supported by the range of the fluctuations around u x and u z that are phase dependent and more dominant at the top of the porous elements that characterize the bed interface (Figure 5c).…”

Section: Model-data Comparisonsupporting

confidence: 72%

“…The numerical results suggest that the VARANS model is able to reproduce the generation, physical length and evolution of the macro vortices, and related modulations in the near bed velocity signals. Furthermore, the qualitative agreement with Corvaro et al [2014] observations also comprises the spatial gradients of near bed vorticity and local Reynolds shear stress (not shown).…”

Section: Model-data Comparisonsupporting

confidence: 63%

“…The model-data comparisons suggest that the VARANS k-numerical scheme is capable of simulating the transient nature of near bed properties from dam break driven flows [e.g., Kikkert et al, 2012Kikkert et al, , 2013 and the fundamental properties characterizing suction/injection events under oscillatory flow [e.g., Corvaro et al, 2014]. Therefore, the numerical model is further employed to investigate the influence of beach permeability and porosity on BL dynamics inside the swash zone.…”

Section: Resultsmentioning

confidence: 99%

“…Corvaro et al [2014] investigated the influence of in/ out flows on nearbed vortical patterns, TKE structure, and fluctuations around the mean flow velocity due Figure 5 shows the bed-parallel (u x ) and bedorthogonal (u z ) velocity components at two different near bed elevations, along one wave length ( Figure 5a). Consistent with Corvaro et al [2014] observations (Figures 5a1-5c1), the numerical model predicts fluctuations (Figures 5b2-5c2) around the mean flow driven by local pressure gradients under such oscillatory flow conditions. These fluctuations are described in Corvaro et al [2014] as standing vortices that induce large scale modulations around the mean flow velocity while they propagate from one interstitial space to the next one in the local direction of the flow.…”

Section: Model-data Comparisonmentioning

confidence: 99%

“…From these and other studies [e.g., Packwood and Peregrine, 1979;Li et al, 2000;Nielsen et al, 2001;Karambas, 2003] it is established that one of the main effects of the infiltrating/exfiltrating flows relates to the mass and momentum transfer that result from these motions, affecting the magnitudes of the bed shear stress and the BL thickness. Additionally, these fluxes are responsible for the suction/injection of turbulence and, consequently, for the thinning/spreading of the BL [Lohmann et al, 2006;Sparrow et al, 2012;Kikkert et al, 2013;Corvaro et al, 2014]. The continuity effect [after Baldock and Nielsen, 2010;Kikkert et al, 2013] denotes the modification of the momentum balance due to losses of water volume in the surface flow that may also indirectly affect the bed shear stress.…”

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: Model-data Comparisonsupporting

confidence: 72%

Section: Model-data Comparisonsupporting

confidence: 63%