Velocity Statistics of Round, Fully Developed, Buoyant Turbulent Plumes

1995 ◽  
Vol 117 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Z. Dai ◽  
L. K. Tseng ◽  
G. M. Faeth
Keyword(s):  
Carbon Dioxide ◽  
Sulfur Hexafluoride ◽  
Mixture Fraction ◽  
Power Spectra ◽  
Reynolds Stresses ◽  
Test Range ◽  
Velocity Statistics ◽  
Present Test ◽  
Integral Scales ◽  
Temporal And Spatial

An experimental study of the structure of round buoyant turbulent plumes was carried out, limited to conditions within the fully developed (self-preserving) portion of the flow. Plume conditions were simulated using dense gas sources (carbon dioxide and sulfur hexafluoride) in a still air environment. Velocity statistics were measured using laser velocimetry in order to supplement earlier measurements of mixture fraction statistics using laser-induced iodine fluorescence. Similar to the earlier observations of mixture fraction statistics, self-preserving behavior was observed for velocity statistics over the present test range (87–151 source diameters and 12–43 Morton length scales from the source), which was farther from the source than most earlier measurements. Additionally, the new measurements indicated that self-preserving plumes are narrower, with larger mean streamwise velocities near the axis (when appropriately scaled) and with smaller entrainment rates, than previously thought. Velocity statistics reported include mean and fluctuating velocities, temporal power spectra, temporal and spatial integral scales, and Reynolds stresses.

Structure of Round, Fully Developed, Buoyant Turbulent Plumes

1994 ◽  
Vol 116 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Z. Dai ◽  
L.-K. Tseng ◽  
G. M. Faeth
Keyword(s):  
Carbon Dioxide ◽  
Experimental Study ◽  
Sulfur Hexafluoride ◽  
Mixture Fraction ◽  
Power Spectra ◽  
Probability Density Functions ◽  
Density Functions ◽  
Spatial Correlations ◽  
Integral Scales ◽  
Temporal And Spatial

An experimental study of the structure of round buoyant turbulent plumes was carried out, emphasizing conditions in the fully developed (self-preserving) portion of the flow. Plume conditions were simulated using dense gas sources (carbon) dioxide and sulfur hexafluoride) in a still air environment. Mean and fluctuating mixture fraction properties were measured using single-and two-point laser-induced iodine fluorescence. The present measurements extended farther from the source (up to 151 source diameters) than most earlier measurements (up to 62 source diameters) and indicated that self-preserving turbulent plumes are narrower, with larger mean and fluctuating mixture fractions (when appropriately scaled) near the axis, than previously thought. Other mixture fraction measurements reported include probability density functions, temporal power spectra, radial spatial correlations and temporal and spatial integral scales.

Velocity Statistics of Plane Self-Preserving Buoyant Turbulent Adiabatic Wall Plumes

1999 ◽  
Author(s):  
R. Sangras ◽  
Z. Dai ◽  
G. M. Faeth
Keyword(s):  
Vertical Wall ◽  
Power Spectra ◽  
Adiabatic Wall ◽  
Wall Boundary Layer ◽  
Velocity Statistics ◽  
Integral Scales ◽  
Turbulent Wall Jets ◽  
Development Region ◽  
Temporal And Spatial ◽  
Turbulent Wall

Abstract Measurements of the velocity properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The experiments involved helium/air mixtures rising along a smooth, plane and vertical wall. Mean and fluctuating streamwise and cross stream velocities were measured using laser velocimetry. Self-preserving behavior was observed 92–156 source widths from the source, yielding smaller normalized plume widths and larger near-wall mean velocities than observations within the flow development region nearer to the source. Unlike earlier observations of concentration fluctuation intensities, which are unusually large due to effects of streamwise buoyant instabilities, velocity fluctuation intensities were comparable to values observed in nonbuoyant turbulent wall jets. The entrainment properties of the present flows approximated self-preserving behavior in spite of continued development of the wall boundary layer. Measurements of temporal power spectra and temporal and spatial integral scales of velocity fluctuations are also reported.

Velocity Statistics of Plane Self-Preserving Buoyant Turbulent Adiabatic Wall Plumes

2000 ◽  
Vol 122 (4) ◽  
pp. 693-700 ◽  
Author(s):  
R. Sangras ◽  
Z. Dai ◽  
G. M. Faeth
Keyword(s):  
Vertical Wall ◽  
Power Spectra ◽  
Adiabatic Wall ◽  
Wall Boundary Layer ◽  
Velocity Statistics ◽  
Integral Scales ◽  
Turbulent Wall Jets ◽  
Development Region ◽  
Temporal And Spatial ◽  
Turbulent Wall

Measurements of the velocity properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The experiments involved helium/air mixtures rising along a smooth, plane, and vertical wall. Mean and fluctuating streamwise and cross-stream velocities were measured using laser velocimetry. Self-preserving behavior was observed 92–156 source widths from the source, yielding smaller normalized plume widths and larger near-wall mean velocities than observations within the flow development region nearer to the source. Unlike earlier observations of concentration fluctuation intensities, which are unusually large due to effects of streamwise buoyant instabilities, velocity fluctuation intensities were comparable to values observed in nonbuoyant turbulent wall jets. The entrainment properties of the present flows approximated self-preserving behavior in spite of continued development of the wall boundary layer. Measurements of temporal power spectra and temporal and spatial integral scales of velocity fluctuations are also reported. [S0022-1481(00)00504-1]

Velocity/Mixture Fraction Statistics of Round, Self-Preserving, Buoyant Turbulent Plumes

1995 ◽  
Vol 117 (4) ◽  
pp. 918-926 ◽  
Author(s):  
Z. Dai ◽  
L. K. Tseng ◽  
G. M. Faeth
Keyword(s):  
Sulfur Hexafluoride ◽  
Gaussian Approximation ◽  
Mixture Fraction ◽  
Turbulence Models ◽  
Test Range ◽  
Radial Gradient ◽  
Gradient Diffusion ◽  
Mass Fluxes ◽  
Normal Manner ◽  
Scalar Variance

An experimental study of the structure of round buoyant turbulent plumes was carried out, limited to conditions in the self-preserving portion of the flow. Plume conditions were simulated using dense gas sources (carbon dioxide and sulfur hexafluoride) in a still and unstratified air environment. Velocity/mixture-fraction statistics, and other higher-order turbulence quantities, were measured using laser velocimetry and laser-induced fluorescence. Similar to earlier observations of these plumes, self-preserving behavior of all properties was observed for the present test range, which involved streamwise distances of 87–151 source diameters and 12–43 Morton length scales from the source. Streamwise turbulent fluxes of mass and momentum exhibited countergradient diffusion near the edge of the flow, although the much more significant radial fluxes of these properties satisfied gradient diffusion in the normal manner. The turbulent Prandtl/Schmidt number, the ratio of time scales characterizing velocity and mixture function fluctuations and the coefficient of the radial gradient diffusion approximation for Reynolds stress, all exhibited significant variations across the flow rather than remaining constant as prescribed by simple turbulence models. Fourth moments of velocity and velocity/mixture fraction fluctuations generally satisfied the quasi-Gaussian approximation. Consideration of budgets of turbulence quantities provided information about kinetic energy and scalar variance dissipation rates, and also indicated that the source of large mixture fraction fluctuations near the axis of these flows involves interactions between large streamwise turbulent mass fluxes and the rapid decay of mean mixture fractions in the streamwise direction.

Mixture Fraction Statistics of Plane Self-Preserving Buoyant Turbulent Adiabatic Wall Plumes

1999 ◽  
Vol 121 (4) ◽  
pp. 837-843 ◽  
Author(s):  
R. Sangras ◽  
Z. Dai ◽  
G. M. Faeth
Keyword(s):  
Large Scale ◽  
Mixture Fraction ◽  
Vertical Wall ◽  
Power Spectra ◽  
Probability Density Functions ◽  
Density Functions ◽  
Adiabatic Wall ◽  
Integral Scales ◽  
Smooth Plane ◽  
Motion Measurements

Measurements of the mixture fraction properties of plane buoyant turbulent adiabatic wall plumes (adiabatic wall plumes) are described, emphasizing conditions far from the source where self-preserving behavior is approximated. The experiments involved helium/air mixtures rising along a smooth, plane and vertical wall. Mean and fluctuating mixture fractions were measured using laser-induced iodine fluorescence. Self-preserving behavior was observed 92–155 source widths above the source, yielding smaller normalized plume widths and near-wall mean mixture fractions than earlier measurements. Self-preserving adiabatic wall plumes mix slower than comparable free line plumes (which have 58 percent larger normalized widths) because the wall prevents mixing on one side and inhibits large-scale turbulent motion. Measurements of probability density functions, temporal power spectra, and temporal integral scales of mixture fraction fluctuations are also reported.

Mixing Structure of Plane Self-Preserving Buoyant Turbulent Plumes

1998 ◽  
Vol 120 (4) ◽  
pp. 1033-1041 ◽  
Author(s):  
R. Sangras ◽  
Z. Dai ◽  
G. M. Faeth
Keyword(s):  
Probability Density ◽  
Mixture Fraction ◽  
Power Spectra ◽  
Probability Density Functions ◽  
Density Functions ◽  
Integral Scales

Measurements of the structure of plane buoyant turbulent plumes are described, emphasizing conditions in the fully developed (self-preserving) portion of the flow. Plumes were simulated using helium/air sources in a still and unstratified air environment. Mean and fluctuating mixture fractions were measured using laser-induced iodine fluorescence. Present measurements extended farther from the source (up to 155 source widths) and had more accurate specifications of plume buoyancy fluxes than past measurements and yielded narrower plume widths and different scaled mean and fluctuating mixture fractions near the plane of symmetry than previously thought. Measurements of probability density functions, temporal power spectra, and temporal integral scales of mixture fraction fluctuations are also reported.

Sulfur hexafluoride F6S + CO2 Carbon dioxide

2006 ◽  
pp. 1-1
Author(s):  
C. J. Wormald ◽  
J.-P. E. Grolier ◽  
J.-C. Fontaine ◽  
K. Sosnkowska-Kehiaian ◽  
H. V. Kehiaian
Keyword(s):  
Carbon Dioxide ◽  
Sulfur Hexafluoride

Ultraviolet Spectral Analysis and Quantitative Detection of Heptafluoroisobutyronitrile (C4F7N) in a C4F7N–Carbon Dioxide (CO2) Gas Mixture

2019 ◽  
Vol 73 (8) ◽  
pp. 917-926 ◽  
Author(s):  
Yin Zhang ◽  
Xiaoxing Zhang ◽  
Chang Liu ◽  
Yi Li ◽  
Zhaolun Cui ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Absorption Spectroscopy ◽  
Density Functional ◽  
Sulfur Hexafluoride ◽  
Detection System ◽  
Spectral Characteristics ◽  
Uv Absorption ◽  
Quantitative Detection ◽  
Gas Mixture ◽  
Uv Absorption Spectroscopy

As an alternative to sulfur hexafluoride (SF6) with great potential for application, heptafluoroisobutyronitrile–carbon dioxide (C4F7N–CO2) gas mixture has been applied in various gas-insulated equipment. The insulation performance of the gas mixture is closely related to the mixing ratio. Therefore, accurate quantification of C4F7N in the C4F7N–CO2 gas mixture has very important engineering significance. At present, there are few reports on the rapid quantitative detection of the concentration of C4F7N in the gas mixture. In this paper, a rapid analytical method for C4F7N concentration based on ultraviolet (UV) absorption spectroscopy is constructed. The UV spectral characteristics of C4F7N molecules are calculated by density functional theory. The appropriate bands that can be detected are determined by analyzing the calculated results. A concentration detection system of C4F7N based on UV absorption spectroscopy is built. Through analysis of the calculated results and experimental results, a quantitative detection method of C4F7N in the C4F7N/CO2 gas mixture is determined. The method can achieve accurate detection of the concentration of the gas mixture in the conventional application range (including 4–10% C4F7N). The coefficient of the determination R2 of the concentration inversion curve reaches 0.999 and the inversion error ratio does not exceed 5%. The related research results provide an important reference for the engineering application of the gas mixture.

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