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 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.

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.

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.

Structure of Turbulent Adiabatic Wall Plumes

1986 ◽  
Vol 108 (4) ◽  
pp. 827-834 ◽  
Author(s):  
M.-C. Lai ◽  
S.-M. Jeng ◽  
G. M. Faeth
Keyword(s):  
Flow Structure ◽  
Large Scale ◽  
Vertical Wall ◽  
Light Sheet ◽  
Mie Scattering ◽  
Wall Structure ◽  
Turbulent Structures ◽  
Adiabatic Wall ◽  
Stable Orientation ◽  
Turbulent Wall

Weakly buoyant turbulent wall plumes were studied for surfaces inclined 0–62 deg from the vertical (stable orientation). The source of buoyancy was carbon dioxide/air mixtures in still air, assuring conserved buoyancy flux. Profiles of mean and fluctuating concentrations and streamwise velocities were measured at several stations along the wall. Flow structure was also observed by Mie scattering from a laser light sheet. Tests with inclined walls showed that low levels of ambient stratification caused the wall plumes to entrain fluid in the horizontal direction, rather than normal to the wall. Structure predictions were made for vertical wall plumes, considering Favre-averaged mixing-length and k–ε–g models of turbulence. Both methods yielded encouraging predictions of flow structure, in spite of the presence of large-scale coherent turbulent structures observed in the flow visualization.

scholarly journals Curvature Effects on Two-dimensional Turbulent Wall Jets along Concave Surfaces

1983 ◽  
Vol 26 (222) ◽  
pp. 2074-2080 ◽  
Author(s):  
Ryoji KOBAYASHI ◽  
Nobuyuki FUJISAWA
Keyword(s):  
Two Dimensional ◽  
Wall Jets ◽  
Curvature Effects ◽  
Turbulent Wall Jets ◽  
Turbulent Wall

Experiments on Flame Flashback in a Quasi-2D Turbulent Wall Boundary Layer for Premixed Methane-Hydrogen-Air Mixtures

2010 ◽  
Author(s):  
Christian Eichler ◽  
Thomas Sattelmayer
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Turbulent Flows ◽  
Turbulent Transport ◽  
Wall Friction ◽  
Evaluation Procedure ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Flame Flashback ◽  
Turbulent Wall

Premixed combustion of hydrogen-rich mixtures involves the risk of flame flashback through wall boundary layers. For laminar flow conditions, the flashback mechanism is well understood and is usually correlated by a critical velocity gradient at the wall. Turbulent transport inside the boundary layer considerably increases the flashback propensity. Only tube burner setups have been investigated in the past and thus turbulent flashback limits were only derived for a fully-developed Blasius wall friction profile. For turbulent flows, details of the flame propagation in proximity to the wall remain unclear. This paper presents results from a new experimental combustion rig, apt for detailed optical investigations of flame flashbacks in a turbulent wall boundary layer developing on a flat plate and being subject to an adjustable pressure gradient. Turbulent flashback limits are derived from the observed flame position inside the measurement section. The fuels investigated cover mixtures of methane, hydrogen and air at various mixing ratios. The associated wall friction distributions are determined by RANS computations of the flow inside the measurement section with fully resolved boundary layers. Consequently, the interaction between flame back pressure and incoming flow is not taken into account explicitly, in accordance with the evaluation procedure used for tube burner experiments. The results are compared to literature values and the critical gradient concept is reviewed in light of the new data.

Erosion By Circular Turbulent Wall Jets

1977 ◽  
Vol 15 (3) ◽  
pp. 277-289 ◽  
Author(s):  
N. Rajaratnam ◽  
B. Berry
Keyword(s):  
Wall Jets ◽  
Turbulent Wall Jets ◽  
Turbulent Wall

Near-Wall Modeling of Plane Turbulent Wall Jets

1997 ◽  
Vol 119 (2) ◽  
pp. 304-313 ◽  
Author(s):  
G. Gerodimos ◽  
R. M. C. So
Keyword(s):  
Boundary Layer ◽  
Outer Region ◽  
Plane Wall ◽  
Equation Modeling ◽  
Wall Jets ◽  
Free Jet ◽  
Turbulent Wall Jets ◽  
Turbulent Wall ◽  
Simple Flows ◽  
Near Wall

In most two-dimensional simple turbulent flows, the location of zero shear usually coincides with that of vanishing mean velocity gradient. However, such is not the case for plane turbulent wall jets. This could be due to the fact that the driving potential is the jet exit momentum, which gives rise to an outer region that resembles a free jet and an inner layer that is similar to a boundary layer. The interaction of a free-jet like flow with a boundary-layer type flow distinguishes the plane wall jet from other simple flows. Consequently, in the past, two-equation turbulence models are seldom able to predict the jet spread correctly. The present study investigates the appropriateness of two-equation modeling; particularly the importance of near-wall modeling and the validity of the equilibrium turbulence assumption. An improved near-wall model and three others are analyzed and their predictions are compared with recent measurements of plane wall jets. The jet spread is calculated correctly by the improved model, which is able to replicate the mixing behavior between the outer jet-like and inner wall layer and is asymptotically consistent. Good agreement with other measured quantities is also obtained. However, other near-wall models tested are also capable of reproducing the Reynolds-number effects of plane wall jets, but their predictions of the jet spread are incorrect.

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