Effects of wall permeability on turbulence

Suga, Kazuhiko; Matsumura, Yasuhiro; Ashitaka, Yu; Tominaga, Satoshi; Kaneda, Masayuki

doi:10.1016/j.ijheatfluidflow.2010.02.023

Cited by 108 publications

(209 citation statements)

References 32 publications

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“…As suggested in figure 2(b), the mean velocity profile over a large range of Re K possesses characteristics of both the impermeable boundary and the highly permeable boundary, with a logarithmic velocity profile above the interface (e.g. Suga et al 2010;Manes, Poggi & Ridolfi 2011a) and an inflection point at the interface (e.g. Goharzadeh, Khalili & Jørgensen 2005;Breugem et al 2006).…”

Section: Flow Characteristics For Re Kmentioning

confidence: 91%

“…The relative intensity of the vertical velocity fluctuations therefore increases while the intensity of the streamwise fluctuations decreases (Breugem et al 2006;Suga et al 2010;Manes et al 2011a), enhancing mass transfer (as seen in figure 1). The observed decrease in streamwise turbulence intensity near the interface is most likely related to a change in turbulent structures in the near-wall region, as Breugem et al (2006) found that the signatures of the large-scale motions, typical for the impermeable boundary, disappear for Re K 1.…”

Section: Flow Characteristics For Re Kmentioning

confidence: 94%

“…The interfacial velocity at the SWI has been suggested to be a function of the shear velocity u * for Re K = O(0.1-1) (Suga et al 2010). Although a clear understanding of the variation of U i /u * with Re K is desirable, the sensitivity of U i to the choice of position of the interface makes determination of U i /u * difficult.…”

Section: Flow Characteristics For Re Kmentioning

confidence: 99%

“…For instance, in some studies the SWI is taken at the absolute top of the obstructive elements (e.g. Goharzadeh et al 2005;Breugem et al 2006;Suga et al 2010), which typically corresponds to the definition in highly permeable boundaries (Nepf 2012). However, others adopt a definition closer to that of an impermeable boundary, positioning the interface within the roughness elements (e.g.…”

Section: Flow Characteristics For Re Kmentioning

confidence: 99%

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The variation of flow and turbulence across the sediment–water interface

2017

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A basic framework characterising the interaction between aquatic flows and permeable sediment beds is presented here. Through the permeability Reynolds number (Re K = √ Ku * /ν, where K is the sediment permeability, u * is the shear velocity and ν is the fluid viscosity), the framework unifies two classical flow typologies, namely impermeable boundary layer flows (Re K 1) and highly permeable canopy flows (Re K 1). Within this range, the sediment-water interface (SWI) is identified as a transitional region, with Re K in aquatic systems typically O(0.001-10). As the sediments obstruct conventional measurement techniques, experimental observations of interfacial hydrodynamics remain extremely rare. The use of refractive index matching here allows measurement of the mean and turbulent flow across the SWI and thus direct validation of the proposed framework. This study demonstrates a strong relationship between the structure of the mean and turbulent flow at the SWI and Re K . Hydrodynamic characteristics, such as the interfacial turbulent shear stress, velocity, turbulence intensities and turbulence anisotropy tend towards those observed in flows over impermeable boundaries as Re K → 0 and towards those seen in flows over highly permeable boundaries as Re K → ∞. A value of Re K ≈ 1-2 is seen to be an important threshold, above which the turbulent stress starts to dominate the fluid shear stress at the SWI, the penetration depths of turbulence and the mean flow into the sediment bed are comparable and similarity relationships developed for highly permeable boundaries hold. These results are used to provide a new perspective on the development of interfacial transport models at the SWI.

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Section: Flow Characteristics For Re Kmentioning

confidence: 91%

Section: Flow Characteristics For Re Kmentioning

confidence: 94%

Section: Flow Characteristics For Re Kmentioning

confidence: 99%

Section: Flow Characteristics For Re Kmentioning

confidence: 99%

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The variation of flow and turbulence across the sediment–water interface

2017

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“…The related studies also found that the distribution of the mean streamwise velocity may change due to the influences of wall roughness [38,77]. The measured profile affected by the wall roughness slightly moves down relative to the profile of the case with smooth wall.…”

Section: Mean Streamwise Velocitymentioning

confidence: 73%

A Short Review on Drag-Reduced Turbulent Flow of Inhomogeneous Polymer Solutions

Kawaguchi

2013

Advances in Mechanical Engineering

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Turbulent drag reduction by additives is an effective approach to save energy in wall turbulence. Improvement of this approach requires a better understanding of the interactions between turbulence and additives including the complex changes in turbulence under various conditions of additives. In this paper we review some recent progress in the investigations of drag reduction in wall turbulence with inhomogeneous polymer solutions via slot-injection and wall-blowing methods. The turbulent statistics characteristics and coherent structures modified by the inhomogeneous polymer additives and the polymer diffusion characteristics in the turbulent boundary layer (TBL) flow and channel flow are discussed in terms of previous experimental and numerical studies. This review also presents a discussion of current limitations and future directions in these areas. Readers may find it helpful in understanding the phenomenon of turbulent drag reduction by inhomogeneous polymer additives and in developing practical applications.

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Vertical dispersion in vegetated shear flows

Rubol

Battiato²,

Barros

2016

Water Resour. Res.

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Canopy layers control momentum and solute transport to and from the overlying water surface layer. These transfer mechanisms strongly dependent on canopy geometry, affect the amount of solute in the river, the hydrological retention and availability of dissolved solutes to organisms located in the vegetated layers, and are critical to improve water quality. In this work, we consider steady state transport in a vegetated channel under fully developed flow conditions. Under the hypothesis that the canopy layer can be described as an effective porous medium with prescribed properties, i.e., porosity and permeability, we model solute transport above and within the vegetated layer with an advection‐dispersion equation with a spatially variable dispersion coefficient (diffusivity). By means of the Generalized Integral Transform Technique, we derive a semianalytical solution for the concentration field in submerged vegetated aquatic systems. We show that canopy layer's permeability affects the asymmetry of the concentration profile, the effective vertical spreading behavior, and the magnitude of the peak concentration. Due to its analytical features, the model has a low computational cost. The proposed solution successfully reproduces previously published experimental data.

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Effects of wall permeability on turbulence

Cited by 108 publications

References 32 publications

The variation of flow and turbulence across the sediment–water interface

The variation of flow and turbulence across the sediment–water interface

A Short Review on Drag-Reduced Turbulent Flow of Inhomogeneous Polymer Solutions

Vertical dispersion in vegetated shear flows

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