Gas Transfer Across a Zero-Shear Surface: A Local Approach

Atmane, Mohamed A.; George, J.

doi:10.1029/gm127p0255

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…(b) is located at (H − y)/ δ = 1. The maximum c rms /(c s − c b ) values were ≈ 0.3, which is in agreement with previous numerical(Magnaudet & Calmet 2006;Herlina & Wissink 2014 and experimental(Atmane & George 2002) results. The lower normalised c rms peak values of ≈0.1-0.2 obtained in the experiments ofHerlina & Jirka (2008) andJanzen et al (2010) indicate a partially contaminated surface, as confirmed by the numerical studies ofKhakpour, Shen & Yue (2011) andWissink et al (2017).…”

supporting

confidence: 92%

Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

et al. 2022

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We present direct numerical simulation results of turbulent open channel flow at bulk Reynolds numbers up to 12 000, coupled with (passive) scalar transport at Schmidt numbers up to 200. Care is taken to capture the very large-scale motions which appear already for relatively modest Reynolds numbers. The transfer velocity at the flat, free surface is found to scale with the Schmidt number to the power ‘ $-1/2$ ’, in accordance with previous studies and theoretical predictions for uncontaminated surfaces. The scaling of the transfer velocity with Reynolds number is found to vary, depending on the Reynolds number definition used. To compare the present results with those obtained in other systems, we define a turbulent Reynolds number at the edge of the surface-influenced layer. This allows us to probe the two-regime model of Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19, 1976, pp. 613–624), which is found to correctly predict that small-scale vortices significantly affect the mass transfer for turbulent Reynolds numbers larger than 500. It is further established that the root mean square of the surface divergence is, on average, proportional to the mean transfer velocity. However, the spatial correlation between instantaneous surface divergence and transfer velocity tends to decrease with increasing Schmidt number and increase with increasing Reynolds number. The latter is shown to be caused by an enhancement of the correlation in high-speed regions, which in turn is linked to the spatial distribution of surface-parallel vortices.

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confidence: 92%

Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

et al. 2022

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“…In agreement with experiments of e.g. Chu & Jirka (1992); Atmane & George (2002); Herlina & Jirka (2008), in the HW14 simulations it was found that the concentration boundary layer thickness δ depends on the level of isotropic turbulence diffusing from below. This turbulence promotes the interchange of unsaturated fluid from the bulk with saturated fluid from the surface.…”

Section: Scaling Of Transfer Velocity With Sc and R Tsupporting

confidence: 89%

“…Magnaudet & Calmet 2006) and is also found in some experiments (e.g. Atmane & George 2002). Some other experiments, however, show c rms peaks as low as 0.1 to 0.2 (e.g.…”

Section: Statistics Of Turbulent Scalar Transportsupporting

confidence: 68%

“…performed by Magnaudet & Calmet (2006) for open-channel flow, while Hasegawa & Kasagi (2008) carried out a hybrid DNS-LES of surface-shear driven mass transfer. Similarly, present experimental techniques still face difficulty in properly resolving the instantaneous scalar and flow properties within the concentration boundary layer (Chu & Jirka 1992;Atmane & George 2002;Variano & Cowen 2013). Hence, only in a limited number of experiments (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of air–water interfacial mass transfer driven by high-intensity isotropic turbulence

Herlina

Wissink

2018

J. Fluid Mech.

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Previous direct numerical simulations (DNS) of mass transfer across the air–water interface have been limited to low-intensity turbulent flow with turbulent Reynolds numbers of $R_{T}\leqslant 500$. This paper presents the first DNS of low-diffusivity interfacial mass transfer across a clean surface driven by high-intensity ($1440\leqslant R_{T}\leqslant 1856$) isotropic turbulent flow diffusing from below. The detailed results, presented here for Schmidt numbers $Sc=20$ and $500$, support the validity of theoretical scaling laws and existing experimental data obtained at high $R_{T}$. In the DNS, to properly resolve the turbulent flow and the scalar transport at $Sc=20$, up to $524\times 10^{6}$ grid points were needed, while $65.5\times 10^{9}$ grid points were required to resolve the scalar transport at $Sc=500$, which is typical for oxygen in water. Compared to the low-$R_{T}$ simulations, where turbulent mass flux is dominated by large eddies, in the present high-$R_{T}$ simulation the contribution of small eddies to the turbulent mass flux was confirmed to increase significantly. Consequently, the normalised mass transfer velocity was found to agree with the $R_{T}^{-1/4}$ scaling, as opposed to the $R_{T}^{-1/2}$ scaling that is typical for low-$R_{T}$ simulations. At constant $R_{T}$, the present results show that the mass transfer velocity $K_{L}$ scales with $Sc^{-1/2}$, which is identical to the scaling found in the large-eddy regime for $R_{T}\leqslant 500$. As previously found for a no-slip interface, also for a shear-free interface the critical $R_{T}$ separating the large- from the small-eddy regime was confirmed to be approximately $R_{T}=500$.

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“…The Figure 6: Experimental and theoretical concentration RMS profiles. Data of [5,19,20]. experiments represented by the light grey cloud (envelope of data of Ref.…”

Section: Mathematical Modelsmentioning

confidence: 99%

Turbulence aspects of mass transfer in the thin interfacial region of the concentration boundary layer in gas–liquid systems

Schulz¹,

Lavin²,

Gonçalves³

2017

Int. J. CMEM

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The quantification of overall mass transfers in gas-liquid systems depends on the spatial evolution of the relevant variables close to the interface of the two phases. When turbulence is present (in the present study the turbulence is considered in the liquid phase), the methods of treating the problem consider the differential form of the momentum and mass conservation equations. The continuous hypothesis that underlies these equations in principle allows verifying the limiting trends very close to the interface. Because the theoretical concepts of turbulence are defined using statistical tools, the mentioned verification depends on the intrinsic definitions used in the statistical approach. In this study the turbulent mass transfer parameters are calculated for the thin region close to the interface based on the tool of random square waves (RSW). Theoretical results are obtained and analyzed in the context of existing experimental data and conceptual discussions of the literature, using a constant 'reduction function', a parameter defined in this methodology. The results of the present analysis show that the RSW method allows obtaining functional trends, as well as indicate the adequacy of using a variable reduction function to better represent reality.

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Gas Transfer Across a Zero-Shear Surface: A Local Approach

Cited by 6 publications

References 9 publications

Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

Simulation of air–water interfacial mass transfer driven by high-intensity isotropic turbulence

Turbulence aspects of mass transfer in the thin interfacial region of the concentration boundary layer in gas–liquid systems

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