Analysis of intercomponent energy transfer in the interaction of oscillating-grid turbulence with an impermeable boundary

McCorquodale, Mark W.; Munro, R. G.

doi:10.1063/1.5007020

Cited by 11 publications

(34 citation statements)

References 29 publications

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“…As a consequence, the particles are completely immersed in the viscous sublayer. Thus, (11) is valid to estimate the onset of our horizontal particle motion. Following Loiseleux et al 38 This is the author's peer reviewed, accepted manuscript.…”

Section: Horizontal Motion and Particle Lift Up Criteria In The Prmentioning

confidence: 95%

“…µ e α ≈ 1 in (10) which substituted in (11), leads for this onset u d = w s ⇐⇒ u δ = νw s d ≈ 2 mm/s (18) and θ ch ≈ 1 18 (19) In figure 9-a, horizontal motion initiation happens with u δ ≥ 2 mm/s. To know which force balances buoyancy in the initiation of vertical motion, parameter A needs to be estimated.…”

Section: Please Cite This Article As Doi:101063/15141943mentioning

confidence: 96%

“…In order to study thoroughly the part turbulence plays in the erosion process, we used a well-known experimental device that is the oscillating grid 7,8 . The flow produced by this device has been widely studied 1,7,[9][10][11][12] . All different studies agree in that far enough from the grid, the mean flow becomes weak enough to be negligible while turbulence appears to be almost isotropic.…”

Section: Introductionmentioning

confidence: 99%

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Sediment erosion in zero-mean-shear turbulence

2020

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Turbulence plays an evident role in particle erosion that in many practical situations superimposes with the action of a mean flow. In this paper, the turbulence effect on particle erosion is studied under zero-mean flow conditions, by using the turbulence generated by an oscillating grid. The stirring grid is located more than two mesh size away from the particle layer. The zero-mean flow below the grid has been qualified by revisiting Matsunaga et al. 1 k − ε model. The turbulence efficiency on the settling/resuspension of the particles is quantified for various turbulence intensities, varying the size, the nature of the particles, and their buoyancy relative to the fluid. We find that the concentrations C of eroded particles collapse fairly well onto a single trend for C ≤ 5 × 10 −2 , when plotted as a function of the ratio between the flux of turbulent kinetic energy (TKE) at the particle bed location and the particle settling flux. Above, the concentrations saturate thus forming a plateau. Particle erosion mechanisms have been investigated in terms of competing forces within an "impulse approach". Horizontal drag versus friction first leads to a horizontal motion followed by a vertical motion resulting from vertical drag and lift versus buoyancy. Particle erosion occurs when both force balances are in favor of motion for a duration of 0.1 to 0.3 Kolmogorov time scale.

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Section: Horizontal Motion and Particle Lift Up Criteria In The Prmentioning

confidence: 95%

Section: Please Cite This Article As Doi:101063/15141943mentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Sediment erosion in zero-mean-shear turbulence

2020

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“…Oscillating grid apparatus have been commonly used in experimental fluid mechanics since the seminal works of 20,21 . Numerous applications can be found in the literature, among which the study of interactions between turbulence and solid impermeable boundaries, 23,24 of turbulence and gas–liquid mass transfer at a free surface, 19,25‐28 in stratified media, 20,21,29,30 or to study the behavior of bubbles, cells, fibers, and flocculation aggregates suspended in a turbulent liquid phase 31‐35 . Oscillating grid stirred tanks are thus tools that allow to generate and study controlled turbulence.…”

Section: Introductionmentioning

confidence: 99%

“…From an historical perspective, the purpose of such setup has mainly been to generate controlled turbulence away from the grid. As a consequence, until recently, 24,40 no study had focused on oscillatory flows generated by the grid motion in and around its swept region, or on how energy is transferred from the oscillatory forcing to turbulence or mean flow.…”

Section: Introductionmentioning

confidence: 99%

POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

et al. 2020

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Oscillating grids are frequently used with water and Newtonian fluids to generate controlled turbulence and mixing. Yet, their use with shear thinning fluids still requires experimental characterization. Proper orthogonal decomposition (POD) is applied to PIV measurements of the flow generated by an oscillating grid in water and a shear thinning dilute polymer solution (DPS) of xanthan gum. The aims are to investigate the ability of POD to isolate periodic flow structures, and to use it to describe the effects of the shear thinning property. A dominance of the low order POD modes is evidenced in DPS. The methods applied in blade stirred tanks to identify oscillatory motion fail here. However, a strong mode coupling in the grid swept region is observed, determined by the working fluid and by an underlying chaotic nature of the flow. Possibilities of reconstructing turbulence properties using high order modes are discussed.

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A method for reducing mean flow in oscillating-grid turbulence

McCorquodale

Munro

2018

Exp Fluids

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Oscillating-grid turbulence (OGT) is an experimental tool that has been widely used to study the role of turbulent fluctuations under conditions of small mean flow. We report experiments to investigate the structure of the turbulent flow produced by an oscillating grid, using velocity measurements obtained through the application of two-dimensional particle image velocimetry in the vertical plane through the centre of the grid. Ensemble averages of the fluid velocity measurements at specific stages of the grid's oscillation indicate that mean flow is induced in OGT by the merging of grid-induced jets close to the tank sidewalls. The installation of an open-ended 'inner box' (with its top edge positioned just below the bottom of the grid's oscillation) is shown to inhibit the merging of the jets, thereby resulting in a reduction in the magnitude of the mean flow within the interior of the inner box region. Measurements of the time-averaged root-mean-square turbulent velocity components and the time-averaged turbulent kinetic energy flux indicate that the installation of the inner box results in turbulence that is in good agreement with the well-established models of OGT across the central 50% of the inner box's width, but that distinct anisotropic regions exist adjacent to the vertical sidewalls. We anticipate that this simple amendment to reduce the mean flow present in OGT can be readily used in future work that utilises OGT to isolate the effects of turbulent fluctuations from those of the mean flow.

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Analysis of intercomponent energy transfer in the interaction of oscillating-grid turbulence with an impermeable boundary

Cited by 11 publications

References 29 publications

Sediment erosion in zero-mean-shear turbulence

Sediment erosion in zero-mean-shear turbulence

POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

A method for reducing mean flow in oscillating-grid turbulence

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