Mass transfer properties in a grid generated turbulent flow: some experimental investigations about the concept of turbulent diffusivity

Lemoine, Fabrice; Antoine, Yan; Wolff, Michel; Lebouché, M.

doi:10.1016/s0017-9310(97)00362-1

Cited by 8 publications

(7 citation statements)

References 10 publications

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“…are generally consistent with previous findings that the gradient-diffusion invalid in the near field region of scalar transport in grid-generated turbulen turbulent flow is still subject to significant anisotropy and inhomogeneity an development has not yet reached the turbulent-diffusive regime [20,32].…”

Section: Turbulent Mass Transportsupporting

confidence: 92%

“…However, the diffusivity D is shown to become more uniform across the section with increasing downstream distance x/M, and the value at the furthest downstream location (i.e., x/M = 11.6) is also closer to the Taylor diffusivity calculated above (i.e., O(10 −4 ), see Figure 10). These results are generally consistent with previous findings that the gradient-diffusion hypothesis is invalid in the near field region of scalar transport in grid-generated turbulence, where the turbulent flow is still subject to significant anisotropy and inhomogeneity and the plume development has not yet reached the turbulent-diffusive regime [20,32].…”

Section: Turbulent Mass Transportsupporting

confidence: 92%

“…Among the few available studies, Nakamura et al [19] performed separate measurements of velocity and concentration fields, as well as theoretical analysis of the cross-correlation between concentration and velocity fluctuations, to study mass diffusion in grid-generated turbulence. Subsequently, an experimental measurement of turbulent scalar flux and turbulent diffusivity was performed in scalar transport from a point source into grid turbulence by Lemoine et al [20] using combined LIF and LDV. Also, Cuthbertson et al [21] investigated the structural development and breakdown of turbulent, round buoyant jets resulting from their interaction with a turbulence patch generated by an oscillating grid.…”

Section: Introductionmentioning

confidence: 99%

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Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Shao

Huang

Wang

et al. 2021

Water

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Cage-based aquaculture has been growing rapidly in recent years. In some locations, cage-based aquaculture has resulted in the clustering of large quantities of cages in fish farms located in inland lakes or reservoirs and coastal embayments or fjords, significantly affecting flow and mass transport in the surrounding waters. Existing studies have focused primarily on the macro-scale flow blockage effects of fish cages, and the complex wake flow and associated near-field mass transport in the presence of the cages remain largely unclear. As a first step toward resolving this knowledge gap, this study employed the combined Particle Image Velocimetry and Planar Laser Induced Fluorescence (PIV-PLIF) flow imaging technique to measure turbulence characteristics and associated mass transport in the near wake of a steady current through an aquaculture cage net panel in parametric flume experiments. In the near-wake region, defined as ~3M (mesh size) downstream of the net, the flow turbulence was observed to be highly inhomogeneous and anisotropic in nature. Further downstream, the turbulent intensity followed a power-law decay after the turbulence production region, albeit with a decay exponent much smaller than reported values for analogous grid-generated turbulence. Overall, the presence of the net panel slightly enhanced the lateral spreading of the scalar plume, but the lateral distribution of the scalar concentration, concentration fluctuation and transverse turbulent scalar flux exhibited self-similarity from the near-wake region where the flow was still strongly inhomogeneous. The apparent turbulent diffusivity estimated from the gross plume parameters was found to be in reasonable agreement with the Taylor diffusivity calculated as the product of the transverse velocity fluctuation and integral length scale, even when the plume development was still transitioning from a turbulent-convective to turbulent-diffusive regime. The findings of this study provide references to the near-field scalar transport of fish cages, which has important implications in the assessment of the environmental impacts and environmental carrying capacity of cage-based aquaculture.

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Section: Turbulent Mass Transportsupporting

confidence: 92%

Section: Turbulent Mass Transportsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Shao

Huang

Wang

et al. 2021

Water

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“…Arcoumanis et al, 1990;Walker, 1987). LIF has been used to investigate fluid mechanics problems ranging from impinging jets to nuclear reactor coolant systems (Crimaldi and Koseff, 2001;Gavelli and Kiger, 2000;Koochesfahani and Dimotakis, 1985;Lemoine et al, 1998;Shlien, 1988;Unger and Muzzio, 1999).…”

Section: Introductionmentioning

confidence: 99%

Pollutant dispersion in a large indoor space: Part 1 - Scaled experiments using a water-filled model with occupants and furniture

et al. 2004

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Scale modeling is a useful tool for analyzing complex indoor spaces. Scale model experiments can reduce experimental costs, improve control of flow and temperature conditions, and provide a practical method for pretesting full-scale system modifications. However, changes in physical scale and working fluid (air or water) can complicate interpretation of the equivalent effects in the full-scale structure. This paper presents a detailed scaling analysis of a water tank experiment designed to model a large indoor space, and experimental results obtained with this model to assess the influence of furniture and people in the pollutant concentration field at breathing height. Theoretical calculations are derived for predicting the effects from losses of molecular diffusion, small scale eddies, turbulent kinetic energy, and turbulent mass diffusivity in a scale model, even without Reynolds number matching. Pollutant dispersion experiments were performed in a water-filled 30:1 scale model of a large room, using uranine dye injected continuously from a small point source. Pollutant concentrations were measured in a plane, using laser-induced fluorescence techniques, for three interior configurations: unobstructed, table-like obstructions, and table-like and figure-like obstructions. Concentrations within the measurement plane varied by more than an order of magnitude, even after the concentration field was fully developed. Objects in the model interior had a significant effect on both the concentration field and fluctuation intensity in the measurement plane. PRACTICAL IMPLICATION: This scale model study demonstrates both the utility of scale models for investigating dispersion in indoor environments and the significant impact of turbulence created by furnishings and people on pollutant transport from floor level sources. In a room with no furniture or occupants, the average concentration can vary by about a factor of 3 across the room. Adding furniture and occupants can increase this spatial variation by another factor of 3.

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“… in the case of an agitated vessel and Gatard in the case of a two-dimensional jet have coupled microconductimetry to a laser Doppler velocimetry (LDV) technique. Lemoine et al. , coupled LDV to laser-induced fluorescence (LIF) and measured the velocity−concentration correlation in a submerged free jet and in a grid-generated turbulence. Siragna 8 coupled LDV to the polarographic method and obtained the axial velocity−concentration correlation in an axisymmetric jet.…”

Section: Introductionmentioning

confidence: 99%

Turbulent Mixing in a Coflowing Liquid Jet

Benayad

Salem

Legrand

2001

Ind. Eng. Chem. Res.

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Mixing in an axisymmetric concentrated KCl solution jet emerging in a less salty coflowing water has been experimentally investigated. This has been achieved by coupling laser Doppler velocimetry to a microconductimetry technique in view of measuring the turbulent fluxes and and deducing the turbulent diffusivity. The cross-correlation coefficient between radial velocity and concentration R cv reaches a maximum value of 0.77 when the one relative to axial velocity R cu gets smaller and does not exceed 0.37 under the same conditions. The total turbulence intensity, global microscale, kinetic energy dissipation rate, and turbulent diffusion coefficient in the radial direction have also been determined. In a jet section, the turbulent diffusion coefficient was found to vary from 180 to 2000 times the KCl molecular diffusivity D m.

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Mass transfer properties in a grid generated turbulent flow: some experimental investigations about the concept of turbulent diffusivity

Cited by 8 publications

References 10 publications

Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Pollutant dispersion in a large indoor space: Part 1 - Scaled experiments using a water-filled model with occupants and furniture

Turbulent Mixing in a Coflowing Liquid Jet

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