Differential diffusion of high-Schmidt-number passive scalars in a turbulent jet

The separate evolution, or differential diffusion, of high-Schmidt-number passive scalars in a turbulent jet is studied experimentally. The two scalars under consideration are disodium fluorescein (Sc ≡ ν/D = 2000) and sulforhodamine 101 (Sc = 5000). The objectives of the research are twofold: to de...

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Veröffentlicht in:Journal of fluid mechanics Jg. 612; S. 439 - 475
Hauptverfasser: LAVERTU, T. M., MYDLARSKI, L., GASKIN, S. J.
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Cambridge, UK Cambridge University Press 10.10.2008
Schlagworte:
Applied sciences
Combustion. Flame
Decay
Energy
Energy. Thermal use of fuels
Exact sciences and technology
Fluid dynamics
Fluid mechanics
Fundamental areas of phenomenology (including applications)
Instrumentation for fluid dynamics
Jets
Kinematic viscosity
Miscellaneous
Physics
Reynolds number
Theoretical studies. Data and constants. Metering
Turbulence
Turbulent flows, convection, and heat transfer
Fluorescence spectroscopy
Turbulent flow
Instrumentation
Optical systems
Combustion
Passive system
Experimental study
Mixing layer
Diffusion flame
Measurement by laser beam
Jets
Scalar fields
Concentration distribution
ISSN:0022-1120, 1469-7645
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Zusammenfassung:The separate evolution, or differential diffusion, of high-Schmidt-number passive scalars in a turbulent jet is studied experimentally. The two scalars under consideration are disodium fluorescein (Sc ≡ ν/D = 2000) and sulforhodamine 101 (Sc = 5000). The objectives of the research are twofold: to determine (i) the Reynolds-number-dependence, and (ii) the radial distribution of differential diffusion effects in the self-similar region of the jet. Punctual laser-induced fluorescence (LIF) measurements were obtained 50 jet diameters downstream of the nozzle exit for five Reynolds numbers (Re ≡ uod/ν = 900, 2100, 4300, 6700 and 10600, where u0 is the jet exit velocity, d is the jet diameter, and ν is the kinematic viscosity) and for radial positions extending from the centreline to the edges of the jet cross-section (0 ≤ r/d ≤ 7.5). Statistics of the normalized concentration difference, Z, were used to quantify the differential diffusion. The latter were found to decay slowly with increasing Reynolds number, with the root mean square of Z scaling as Zrms ≡ 〈Z2〉1/2 ∝ Re−0.1, (or alternatively 〈Z2〉 ∝ Re−0.2). Regardless of Reynolds number, differential diffusion effects were found to increase away from the centreline. The increase in differential diffusion effects with radial position, along with their increase with decreasing Reynolds number, support the hypothesis of increased differential diffusion at interfaces between the jet and ambient fluids. Power spectral densities of Z were also studied. These spectra decreased with increasing wavenumber – an observation attributed to the decay of the scalar fluctuations in a turbulent jet. Furthermore, these spectra showed that significant differential diffusion effects persist at scales larger than the Kolmogorov scale, even for moderately high Reynolds numbers.
Bibliographie:ark:/67375/6GQ-V8VDX4VS-N
ArticleID:00322
istex:94FF0091370475F633CF7BADE84D5A6C35870147
PII:S0022112008003224
SourceType-Scholarly Journals-1
ObjectType-Feature-1
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ObjectType-Article-2
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ISSN:0022-1120
1469-7645
DOI:10.1017/S0022112008003224