Turbulent mass transfer rates to a wall for large Schmidt numbers

Shaw, Dudley A.; Hanratty, Thomas J.

doi:10.1002/aic.690230106

Cited by 192 publications

(151 citation statements)

References 11 publications

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“…In contrast, the desorption rate a ds in (34) does not affect the exchange between the water column and the sediment layer. This is not so for a very thin layer and for strong turbulence in the water or for a small distribution coefficient (see (32)).…”

Section: One-layer Model Of Bed Sediment Contaminationmentioning

confidence: 88%

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Migration of radioactivity in multi-fraction sediments

et al. 2017

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A new 3D radioactivity transport model coupled with multiscale circulation and multi-fractional sediment transport modules is presented. The sediment transport module simulates the transport of a mixture of one cohesive sediment fraction and a number of fractions of non-cohesive sediments of different sizes and densities. The model of radionuclide transport describes the key transport and exchange processes in the system of water-suspended and bottom multi-fraction sediments. Two-step kinetics with two successive reversible fast and slow reactions is used in the model. A noticeable feature of the model is approximation of the sediment and contamination profiles in the bed by multiple well-mixed layers to describe the vertical migration of radioactivity within bottom sediments due to erosion/deposition, molecular diffusion and bioturbation. The model accurately reproduced a laboratory experiment on the uptake of radiocesium by lake sediments. An analytical solution describing mutual adjustment of the concentrations of radioactivity in the pore water and in the multi-fraction sediment showed that activity was redistributed between different fractions of sediments far slower than between water and the total concentration in the sediment. The extended one-layer model of bottom contamination of multi-fraction sediments was derived from a general model and compared with a multilayer model. It was found, however, that the one-layer approximation was not capable of correctly predicting the inventory due to the fact that one-layer averaged concentration can essentially differ from the near-surface value in the multi-layer model. Radionuclide 123Environ Fluid Mech (2017) 17:1207-1231 DOI 10.1007 transport in channel with bottom depression was simulated to estimate the effects of erosion/deposition and the multi-fractionality of sediments on the transport process. It was shown that these factors affect the distribution of sediments by forming local maxima and minima of activity at the beginning and end of the depression, respectively, due to the redistribution of contaminated bottom sediments by flow. The developed model can also be used to simulate the transport of a wide class of toxic substances sorbed on sediments.

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Section: One-layer Model Of Bed Sediment Contaminationmentioning

confidence: 88%

“…Unlike other radioactivity transport models [2,11], the exchange rate W pw ð0;1Þ (mass transfer coefficient [7]) is estimated by boundary layer theory [34] and corrected for surface roughness [10] as…”

Section: The Equations Of Radionuclide Transportmentioning

confidence: 99%

Migration of radioactivity in multi-fraction sediments

et al. 2017

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“…Usually there is a simple power-law dependence on SC with an index of around -0.7 (e.g. Harriott and Hamilton 1965;Shaw and Hanratty 1977). An elegant asymptotic analysis by Stewart (1987) for high SC and Re shows that two terms in SC are significant.…”

Section: CMmentioning

confidence: 99%

“…An elegant asymptotic analysis by Stewart (1987) for high SC and Re shows that two terms in SC are significant. He fits the Shaw and Hanratty (1977) It should be noted that when using Eq. 25 in Eq.…”

Section: CMmentioning

confidence: 99%

Anomalous mass transfer of phosphate on coral reef flats

Bilger¹,

Atkinson²

1992

Limnology & Oceanography

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To estimate a maximal rate of phosphate (P) uptake into coral reef-flat communities, we introduce analogies between fluid flow in pipes and water flow over coral reef flats. On the basis of results from engineering studies of mass transfer in pipes, the best estimate of the Stanton number (St,, a dimensionless number giving the ratio of uptake rate to the rate of advection of the substance past the uptake surface) for P uptake into a sample reef flat is 5 x 10d5. Field observations yield a value of at least 1.7 x 10-3, a factor of 40 higher. This very large enhancement is due in part to wave surge but also could be due to the difference between the nature of the biotic surfaces and that of the engineering surfaces. The engineering data have been obtained for simple geometries with low ratios of wetted area to projected surface area. It is likely that much of the enhancement arises from the large ratio of wetted to projected area for the coral reef-flat community and the fractal nature of this surface.

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“…The eddy diffusivity for momentum and the eddy diffusivity for mass are related through the turbulent Schmidt number Sc t ϭ E t /D t , where E t is the turbulent diffusion coefficient for momentum transfer. Several different algebraic turbulence models for E t have been proposed (Reichardt 1951;Van Driest 1956;Shaw and Hanratty 1977). All models are empirical, depict similar vertical distance dependence of E t , and display a common rapid decrease in E t as the solid surface is approached (Fig.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Universal scaling of dissolved oxygen distribution at the sediment-water interface: A power law

et al. 2005

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Dissolved oxygen (DO) distribution at the sediment-water interface of a flow over a smooth bed is investigated for Reynolds numbers Ͼ360 and Ͻ4,090. These conditions are commonly encountered in streams, wetlands, and lakes. A power-law scaling of DO distribution is derived and compared with experimental data. The scaling analysis is based on DO flux at the sediment-water interface in a turbulent flow. The power-law model with diffusive sublayer thickness (DSLT) as a fitting parameter agrees well with the data over the investigated range of Reynolds numbers. Using the proposed power-law model with a limited number of DO and flow properties away from the sediment-water interface provides the distribution of DO concentrations and corresponding DSLT at a submillimeter resolution. The estimate of DSLT is, on average, 30% lower than the traditional estimate, defined as a thin fluid layer bounded at the lower boundary by a sediment bed and extended upward in the main water column to where a bulk DO concentration intersects with a linear DO gradient at the bed.The transport processes across the sediment-water interface are of fundamental importance to biological and chemical processes in streams, rivers, and lakes (Boudreau and Jørgensen 2001). In most cases, researchers are concerned about quantifying the distribution and corresponding flux of a particular substance at the sediment-water interface. The dissolved oxygen (DO) concentration in water has been considered one of the most important ecological parameters determining the water quality and associated biological composition of aquatic environments. The sediments, being a repository for decaying biological material with a large organic content, are a major contributor to the DO reduction in the water column.Significant laboratory and field measurements have been devoted to addressing the DO transport process at the sediment-water interface (e.g., Jørgensen and Des Marais 1990; Mackenthun and Stefan 1998;Røy et al. 2002). Microstructure DO measurements with microsensors (e.g., Jørgensen and Revsbech 1985;Lorke et al. 2003;Røy et al. 2004) have been very instrumental in the advancement of theories and models fundamental to the DO transport at the sedimentwater interface. Knowledge of the characteristics of the diffusive sublayer thickness (DSLT) for the DO transport and corresponding DO distribution at the sediment-water interface is crucial in benthic ecology. The difficulty in the characterization of the diffusive sublayer lies in its thinness, usually Ͻ5 mm, and the proximity of a solid boundary.

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Turbulent mass transfer rates to a wall for large Schmidt numbers

Cited by 192 publications

References 11 publications

Migration of radioactivity in multi-fraction sediments

Migration of radioactivity in multi-fraction sediments

Anomalous mass transfer of phosphate on coral reef flats

Universal scaling of dissolved oxygen distribution at the sediment-water interface: A power law

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