Transport of a passive scalar at a shear-free boundary in fully developed turbulent open channel flow

Handler, R.; Saylor, J. R.; Leighton, R. I.; Rovelstad, Amy L.

doi:10.1063/1.870123

Cited by 85 publications

(96 citation statements)

References 36 publications

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“…For open channel flow, DNS calculations (e.g. Handler et al 1999;Khakpour et al 2011) have shown the effect of hairpin vortical structures on scalar transport. In the present case, as described above, only relatively small tube-like structures were found and, due to the shear that was induced by the no-slip boundary conditions, no clear instantaneous correlation could be established with the gas transfer.…”

Section: Numerical Aspectsmentioning

confidence: 99%

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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Section: Numerical Aspectsmentioning

confidence: 99%

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

Herlina

Wissink

2016

J. Fluid Mech.

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“…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. These studies show a number of important features such as the correlation between the vortices ejected from the bottom region and the near-surface concentration field.…”

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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“…Handler et al 7 compared the behavior of open channel flow with Neumann and Dirichlet boundary conditions on a passive scalar at the free surface. They found that variations of the surface flux in the Dirichlet case were much larger than variations of surface concentration when a Neumann condition was used.…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of stably stratified open channel flow

2005

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Large eddy simulation has been used to study flow in an open channel with stable stratification imposed at the free surface by a constant heat flux and an adiabatic bottom wall. This leads to a stable pycnocline overlying a well-mixed turbulent region near the bottom wall. The results are contrasted with studies in which the bottom heat flux is nonzero, a difference analogous to that between oceanic and atmospheric boundary layers. Increasing the friction Richardson number, a measure of the relative importance of the imposed surface stratification with respect to wall-generated turbulence, leads to a stronger, thicker pycnocline which eventually limits the impact of wall-generated turbulence on the free surface. Increasing stratification also leads to an increase in the pressure-driven mean streamwise velocity and a concomitant decrease in the skin friction coefficient, which is, however, smaller than in the previous channel flow studies where the bottom buoyancy flux was nonzero. It is found that the turbulence in any given region of the flow can be classified into three regimes ͑unstratified, buoyancy-affected, and buoyancy-dominated͒ based on the magnitude of the Ozmidov length scale relative to a vertical length characterizing the large scales of turbulence and to the Kolmogorov scale. Since stratification does not strongly influence the near-wall turbulent production in the present configuration, the behavior of the buoyancy flux, turbulent Prandtl number, and mixing efficiency is qualitatively different from that seen in stratified shear layers and in channel flow with fixed temperature walls, and, furthermore, collapse of quantities as a function of gradient Richardson number is not observed. The vertical Froude number is a better measure of stratified turbulence in the upper portion of the channel where buoyancy, by providing a potential energy barrier, primarily affects the transport of turbulent patches generated at the bottom wall. The characteristics of free-surface turbulence including the kinetic energy budget and pressure-strain correlations are examined and found to depend strongly on the surface stratification.

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Transport of a passive scalar at a shear-free boundary in fully developed turbulent open channel flow

Cited by 85 publications

References 36 publications

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

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

Direct numerical simulation of turbulent scalar transport across a flat surface

Large eddy simulation of stably stratified open channel flow

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