The role of free-surface turbulence and surfactants in air–water gas transfer

McKenna, Sean P.; McGillis, Wade R.

doi:10.1016/j.ijheatmasstransfer.2003.06.001

Cited by 152 publications

(167 citation statements)

References 27 publications

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“…Non-intrusive optical measurement techniques such as Particle Image Velocimetry (PIV) have been used in order to understand the near surface hydrodynamics (e.g. Tamburrino & Gulliver 2002;Banerjee et al 2004;McKenna & McGillis 2002, 2004bSugihara & Tsumori 2005;Turney & Banerjee 2013), while Laser Induced Fluorescence (LIF) enabled visualization of the gas concentration fields (e.g Wolff & Hanratty 1994;Münsterer et al 1995;Schladow et al 2002;Woodrow & Duke 2002;Herlina & Jirka 2004;Walker & Peirson 2008). Various research groups (such as Lu & Hetsroni (1995); Handler et al (1999); Nagaosa (1999); Yamamoto et al (2001)) conducted direct numerical simulations (DNS) of passive heat/mass transfer across the free surface of an open-channel flow.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of turbulent scalar transport across a flat surface

Herlina

Wissink

2014

J. Fluid Mech.

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To elucidate the physical mechanisms that play a role in the interfacial transfer of atmospheric gases into water, a series of direct numerical simulations of mass transfer across the air-water interface driven by isotropic turbulence diffusing from below has been carried out for various turbulent Reynolds numbers (R T = 84, 195, 507). To allow a direct (unbiased) comparison of the instantaneous effects of scalar diffusivity, in each of the DNS up to six scalar advection-diffusion equations with different Schmidt numbers were solved simultaneously. As far as the authors are aware this is the first simulation that is capable to accurately resolve the realistic Schmidt number, Sc = 500, that is typical for the transport of atmospheric gases such as oxygen in water. For the range of turbulent Reynolds numbers and Schmidt numbers considered, the normalized transfer velocity K L was found to scale with R − 1 /2 T and Sc − 1 /2 , which indicates that the largest eddies present in the isotropic turbulent flow introduced at the bottom of the computational domain tend to determine the mass transfer. The K L results were also found to be in good agreement with the surface divergence model of McCready, Vassiliadou & Hanratty (AIChE J., vol. 32, 1986, pp. 1108-1115 when using a constant of proportionality of 0.525. Although close to the surface large eddies are responsible for the bulk of the gas transfer, it was also observed that for higher R T the influence of smaller eddies becomes more important.

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Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of turbulent scalar transport across a flat surface

Herlina

Wissink

2014

J. Fluid Mech.

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“…With increasing amounts of surfactants (for example organic substances or chemical surfactants) greater tangential stresses occur and the turbulent eddies near the surface become progressively damped (see Davies 1972) Mass transfer across a severely contaminated water surface 667 leading to a significant decrease in the transfer velocity K L . Experiments in grid-stirred tanks showed that with a surface covered by monolayers a reduction in K L up to 80 % is observed compared with clean conditions (see, e.g., Asher & Pankow 1986;McKenna & McGillis 2004). The infrared images of Flack, Saylor & Smith (2001) and Lee & Saylor (2010), for buoyancy-driven mass transfer, show how the presence of surfactants dramatically changes the convective structures immediately beneath the surface.…”

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Isotropic-turbulence-induced mass transfer across a severely contaminated water surface

Herlina

Wissink

2016

J. Fluid Mech.

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Direct numerical simulations were performed to investigate the effect of severe contamination on interfacial gas transfer in the presence of isotropic turbulence diffusing from below. A no-slip boundary condition was employed at the interface to model the severe contamination effect. The influence of both Schmidt number (Sc) and turbulent Reynolds number (R T ) on the transfer velocity (K L ) was studied. In the range from Sc = 2 up to Sc = 500 it was found that K L ∝ Sc −2/3 , which is in agreement with predictions based on solid-liquid transport models, see e.g. Davies (1972, Turbulence Phenomena, Academic). For similar R T , the transfer velocity was observed to reduce significantly compared with the free-slip conditions. The reduction becomes more pronounced with increasing Schmidt number. Similar to the observation for free-slip conditions made by Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19 (6), 1976, pp. 613-624), the normalized K L in the present no-slip case was also found to depend on R −1/2 T and R −1/4 T for small and large turbulent Reynolds numbers, respectively.

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“…However, the existence of a unique and universal wind-k relationship for all systems is highly questionable given that for any wind speed, its effect on gas exchange is unlikely to be the same in the ocean and, for example, in a small kettle lake. Moreover, many studies have shown that other factors will affect k, such as wind fetch (Frost and Upstill-Goddard 2002;Borges et al 2004;Guérin et al 2007), tidal currents (Borges et al 2004;Zappa et al 2007), rainfall (Ho et al 1997(Ho et al , 2007, microscale breaking waves (Zappa et al 2004), thermal convection (Schladow et al 2002;Eugster et al 2003), organic matter or suspended matter (Abril et al 2009;Calleja et al 2009), and surfactants (Frew et al 1990;McKenna and McGillis 2004).…”

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The relationship between near‐surface turbulence and gas transfer velocity in freshwater systems and its implications for floating chamber measurements of gas exchange

Vachon

Prairie

Cole

2010

Limnology & Oceanography

224

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We performed a series of gas exchange measurements in 12 diverse aquatic systems to develop the direct relationship between near-surface turbulence and gas transfer velocity. The relationship was log-linear, explained 78% of the variation in instantaneous gas transfer velocities, and was valid over a range of turbulent energy dissipation rates spanning about two orders of magnitude. Unlike wind-based relationships, our model is applicable to systems ranging in size from less than 1 km 2 to over 600 km 2 . Gas fluxes measured with our specific model of floating chambers can be grossly overestimated (by up to 1000%), particularly in low-turbulence conditions. In high-turbulence regimes, flux overestimation decreases to within 50%. Direct measurements of turbulent energy dissipation rate provide reliable estimation of the associated gas transfer velocity even at short temporal and spatial scales.

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The role of free-surface turbulence and surfactants in air–water gas transfer

Cited by 152 publications

References 27 publications

Direct numerical simulation of turbulent scalar transport across a flat surface

Direct numerical simulation of turbulent scalar transport across a flat surface

Isotropic-turbulence-induced mass transfer across a severely contaminated water surface

The relationship between near‐surface turbulence and gas transfer velocity in freshwater systems and its implications for floating chamber measurements of gas exchange

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