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 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.

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.

Mean and Fluctuating Radiation Properties of Nonpremixed Turbulent Carbon Monoxide/Air Flames

1989 ◽  
Vol 111 (4) ◽  
pp. 1021-1030 ◽  
Author(s):  
M. E. Kounalakis ◽  
J. P. Gore ◽  
G. M. Faeth
Keyword(s):  
Carbon Monoxide ◽  
Probability Density ◽  
Mixture Fraction ◽  
Power Spectra ◽  
Probability Density Functions ◽  
Stochastic Simulations ◽  
Density Functions ◽  
Spectral Radiation ◽  
Temporal Correlations ◽  
Temporal Properties

Mean and fluctuating spectral radiation intensities were measured for horizontal chordlike paths through turbulent nonpremixed carbon monoxide/air flames. Measurements in the 2700 nm radiation band of carbon dioxide revealed radiation fluctuations exceeding 50 percent in some locations even though mean radiation levels were not strongly influenced by turbulence/radiation interactions. Both time-independent and time-dependent stochastic simulations were developed to treat turbulence/radiation interactions as well as the temporal properties of flame radiation. The stochastic simulations were based on the laminar flamelet concept to relate scalar properties to mixture fracture, methods analogous to statistical time-series techniques to treat the probability density functions and spatial and temporal correlations of mixture fraction along the radiation path, and a narrow-band radiation model. The simulations yielded encouraging predictions of mean and fluctuating values, probability density functions, and temporal power spectra of spectral radiation intensities.

Investigation of the Flopping Regime of Two-, Three-, and Four-Plate Arrays

2000 ◽  
Vol 122 (4) ◽  
pp. 677-682 ◽  
Author(s):  
D. W. Guillaume ◽  
J. C. LaRue
Keyword(s):  
Probability Density ◽  
Pressure Coefficient ◽  
Power Spectra ◽  
Probability Density Functions ◽  
Base Pressure ◽  
Density Functions ◽  
Hot Wire ◽  
Periodic Fluctuations ◽  
Plate Array

The variation of the base pressure coefficient (Cp) and the characteristics of the power spectra of the velocity for arrays of two-, three- and four-plates aligned normal to the flow are presented. The wakes downstream of the plates in the array are shown to exhibit behavior that varies between stable modes, flopping and quasi-stable behavior depending on the s/t distance (where s is the spacing between the top and bottom surfaces of adjacent plates and t is the thickness of the plate). For the two and three-plate arrays with s/t=0.25, peaks in the power spectra of about 48.2 and 98.1 Hz which correspond to Strouhal numbers of 0.06 and 0.11 are observed. For the four-plate array with s/t=0.192, no clear peaks are visible. Probability density functions of uncalibrated hot-wire signals show that the peaks in the power do not correspond to continuously periodic fluctuations. [S0098-2202(00)00604-0]

Noise and Repeatability of Odorant Gas Sensors in an E-Nose

2011 ◽  
pp. 102-124 ◽  
Author(s):  
Fengchun Tian ◽  
Simon X. Yang ◽  
Xuntao Xu ◽  
Tao Liu
Keyword(s):  
Feature Extraction ◽  
Probability Density ◽  
Electronic Nose ◽  
Power Spectra ◽  
Theoretical Background ◽  
Probability Density Functions ◽  
Density Functions ◽  
Processing Methods ◽  
Extraction Algorithm ◽  
The Impact

The impact of the characteristics of the sensors used for electronic nose (e-nose) systems on the repeatability of the measurements is considered. The noise performance of the different types of sensors available for e-nose utilization is first examined. Following the theoretical background, the probability density functions and power spectra of noise from real sensors are presented. The impact of sensor imperfections including noise on repeatability forms the basis of the remainder of the chapter. The impact of the sensors themselves, the effect of data pre-processing methods, and the feature extraction algorithm on the repeatability are considered.

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.

Radial, Turbulent Flow of a Fluid Between Two Coaxial Disks

1989 ◽  
Vol 111 (4) ◽  
pp. 378-383 ◽  
Author(s):  
J. S. Ervin ◽  
N. V. Suryanarayana ◽  
Hon Chai Ng
Keyword(s):  
Experimental Study ◽  
Average Velocity ◽  
Flow Characteristics ◽  
Probability Density Functions ◽  
Energy Spectra ◽  
Density Functions ◽  
Reynolds Stresses ◽  
Law Of The Wall ◽  
A Value ◽  
Reverse Transition

An experimental study to determine the flow characteristics of an incompressible fluid in turbulent, radially outward flow between two coaxial, stationary disks was conducted employing a split film anemometer probe. Instantaneous velocity components in the radial and axial directions were measured; from these measurements, average velocity profiles, turbulence intensities, Reynolds stresses, energy spectra and probability density functions for the fluctuating components were computed. It is observed that the law of the wall may not be applicable everywhere. A criterion established earlier for reverse transition to laminar flow may be valid with a value of the constant smaller than suggested. A few other aspects of the flow are also discussed.

scholarly journals The GF Convection Parameterization: recent developments, extensions, and applications

2020 ◽  
Author(s):  
Saulo R. Freitas ◽  
Georg A. Grell ◽  
Haiqin Li
Keyword(s):  
Chemical Constituents ◽  
Deep Convection ◽  
Cloud Microphysics ◽  
Probability Density Functions ◽  
Vertical Layer ◽  
Spatial Correlations ◽  
Recent Developments ◽  
Temporal And Spatial ◽  
New Feature ◽  
Convection Parameterization

Abstract. We detail recent developments in the GF (Grell and Freitas, 2014, Freitas et al., 2018) convection parameterization and applications. The parameterization has been extended to a trimodal spectral size to simulate the interaction and transition from shallow, congestus and deep convection regimes. Another main new feature is the inclusion of a closure for non-equilibrium convection that resulted in a substantial gain of realism in the simulation of the diurnal cycle of convection, mainly associated with boundary layer forcing over the land. Additional changes include the transport of momentum, the use of three Probability Density Functions (PDF's) to describe the normalized vertical mass flux profiles from deep, congestus, and shallow plumes (respectively) in the grid box, and the option of using temporal and spatial correlations to stochastically perturb PDF's, momentum transport and the closures. Cloud water detrainment is proportional to mass detrainment and in-cloud hydrometeor mixing ratio, and transport of chemical constituents (including wet deposition) can be treated inside the GF scheme. Transport is handled in flux form and is mass conserving. Finally, the cloud microphysics has been extended to include the ice phase to simulate the conversion from liquid water to ice in updrafts with resulting additional heating release, and the melting from snow to rain within a user-specified melting vertical layer.

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]

Sign in / Sign up

Export Citation Format

Share Document