Turbulence Intensity Distribution for Flow Along a Streamwise External Corner

2002 ◽  
Author(s):  
Khalid A. M. Moinuddin ◽  
Peter N. Joubert ◽  
Min S. Chong
Keyword(s):  
Secondary Flow ◽  
Turbulence Intensity ◽  
Leading Edge ◽  
Two Dimensional ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
General Behaviour ◽  
Flow Measurements ◽  
Square Duct ◽  
Normal Distance

This work continues the studies of Moinuddin et al. [1], where experiments were performed on a streamwise external corner. The streamwise development of turbulent boundary layer over an external corner (chine) is influenced by secondary flow which is driven three-dimensionally. The direct effect of this secondary flow is to increase the drag force. Here secondary flow, which is known as Prandtl’s second kind, is induced by inequality of Reynolds stresses around the corner. This flow is expected to exhibit symmetry about the corner bisector. Moinuddin et al. [2,3] have established the symmetry of this flow based upon mean flow measurements. Normal wire measurements for the streamwise turbulence intensity profiles u′2+, measured at about Reθ 5700 and 4.7 m from the model leading edge, are presented in this paper. Mean flow measurements show excellent agreement between Pitot tube and normal wire measurements. Comparisons are made for u′2+, profiles at equal spanwise distance, from the corner, on both surfaces. The profiles agree quite well having nominal deviation depending on spanwise and normal distance from the corner. Isointensity contours also depict symmetrical turbulence distribution. It is also revealed that far from the corner, turbulence profiles agree well with the standard two-dimensional turbulence profile. The measurements agrees with the general behaviour expected from this kind of flow as reported by Xu & Pollard [4] from their LES calculation of flow in an annular square duct.

Secondary Flow Measurements in a Turbine Cascade With High Inlet Turbulence

1992 ◽  
Vol 114 (1) ◽  
pp. 173-183 ◽  
Author(s):  
D. G. Gregory-Smith ◽  
J. G. E. Cleak
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Region ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Measurements ◽  
Frequency Spectra ◽  
The Mean ◽  
End Wall

Measurements of the mean and turbulent flow field have been made in a cascade of high turning turbine rotor blades. The inlet turbulence was raised to 5 percent by a grid placed upstream of the cascade, and the secondary flow region was traversed within and downstream of the blades using a five-hole probe and crossed hot wires. Flow very close to the end wall was measured using a single wire placed at several orientations. Some frequency spectra of the turbulence were also obtained. The results show that the mean flow field is not affected greatly by the high inlet turbulence. The Reynolds stresses were found to be very high, particularly in the loss core. Assessment of the contributions to production of turbulence by the Reynolds stresses shows that the normal stresses have significant effects, as do the shear stresses. The calculation of eddy viscosity from two independent shear stresses shows it to be fairly isotropic in the loss core. Within the blade passage, the flow close to the end wall is highly skewed and exhibits generally high turbulence. The frequency spectra show no significant resonant peaks, except for one at very low frequency, attributable to an acoustic resonance.

Secondary Flow Measurements in a Turbine Cascade With High Inlet Turbulence

1990 ◽  
Author(s):  
D. G. Gregory-Smith ◽  
J. G. E. Cleak
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Flow Region ◽  
Shear Stresses ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Measurements ◽  
Frequency Spectra ◽  
The Mean ◽  
End Wall

Measurements of the mean and turbulent flow field have been made in a cascade of high turning turbine rotor blades. The inlet turbulence was raised to 5% by a grid placed upstream of the cascade, and the secondary flow region was traversed within and downstream of the blades using a 5 hole probe and crossed hot-wires. Flow very close to the end wall was measured using a single wire placed at several orientations. Some frequency spectra of the turbulence were also obtained. The results shows that the mean flow field is not affected greatly by the high inlet turbulence. The Reynolds stresses were found to be very high, particularly in the loss core. Assessment of the contributions to production of turbulence by the Reynolds stresses show that the normal stresses have significant affects as well as the shear stresses. The calculation of eddy viscosity from two independent shear stresses show it to be fairly isotropic in the loss core. Within the blade passage, the flow close to the end wall is highly skewed and exhibits generally high turbulence. The frequency spectra show no significant resonant peaks, except for one at very low frequency, attributable to an acoustic resonance.

Turbulence Structures of Leading Edge Film Cooling Jets

2000 ◽  
Author(s):  
Sabine Ardey ◽  
Stefan Wolff ◽  
Leonhard Fottner
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Suction Side ◽  
Pressure Side ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Turbulence Structures ◽  
Injection Zone

For a better understanding of the turbulence structures attached to film cooling jets, mean flow velocities and turbulent fluctuations were measured by means of 3D hot wire anemometry in the injection zone of a linear, large scale, high pressure turbine cascade with leading edge film cooling. Near the stagnation point, the blades are equipped with one row of film cooling holes each on the suction and pressure side. Two basically different coolant jet situations are compared: On the suction side the jet features the ordinary kidney vortex. On the pressure side, the jet separates completely from the blade surface since it is located above a large recirculation zone created by a locally adverse pressure gradient and a flow separation near the pressure side injection. The measured Reynolds stresses were analyzed with regard to turbulence production and diffusion. The Bousinesque Hypothesis was tested and could not be confirmed. It was found that the turbulence is highly anisotropic. In addition to the brief description of the experimental set up and the acquired data, given in this paper, the complete information are published as a test case (Ardey and Fottner, 1998) that is directly accessible via internet at: http://www.unibw-muenchen.de/campus/LRT12/welcome.html

Effect of a Simulated Free Surface on the Wake of a Slender Body

1986 ◽  
Vol 30 (04) ◽  
pp. 242-255
Author(s):  
P. Mitra ◽  
W. Neu ◽  
J. Schetz
Keyword(s):  
Free Surface ◽  
Turbulent Flow ◽  
Normal Component ◽  
Image Plane ◽  
Axisymmetric Body ◽  
Transverse Component ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Measurements ◽  
The Mean

Turbulent flow measurements were performed in the wake of a slender axisymmetric body in the presence of a flat plate strut and an image plane crudely representing the "rigid lid" approximation to a free surface. The tests were performed in a wind tunnel at a nominal Reynolds number of 6.0 ⨯ 105. A Yawhead probe was used for the mean flow measurements, and a Constant Temperature Anemometer System with an x-wire probe was used to obtain the turbulent flow characteristics. The presence of the image plane was found to increase the velocity defect and the static pressure as the image plane was approached. A redistribution among the various components of velocity fluctuations was noted near the image plane. The transverse component was enhanced at the expense of the normal component. The image plane also was found to influence the magnitudes and radial spread of turbulence intensities and Reynolds stresses. Some interactions between the wake of the axisymmetric body and that of the plate strut were observed. Overall, the mean velocities and the turbulence quantities indicated symmetry about the image plane throughout the wake.

scholarly journals Evolution and structure of sink-flow turbulent boundary layers

2001 ◽  
Vol 428 ◽  
pp. 1-27 ◽  
Author(s):  
M. B. JONES ◽  
IVAN MARUSIC ◽  
A. E. PERRY
Keyword(s):  
Boundary Layers ◽  
Velocity Profiles ◽  
Turbulent Boundary Layers ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Law Of The Wall ◽  
The Mean ◽  
Logarithmic Law

An experimental and theoretical investigation of turbulent boundary layers developing in a sink-flow pressure gradient was undertaken. Three flow cases were studied, corresponding to different acceleration strengths. Mean-flow measurements were taken for all three cases, while Reynolds stresses and spectra measurements were made for two of the flow cases. In this study attention was focused on the evolution of the layers to an equilibrium turbulent state. All the layers were found to attain a state very close to precise equilibrium. This gave equilibrium sink flow data at higher Reynolds numbers than in previous experiments. The mean velocity profiles were found to collapse onto the conventional logarithmic law of the wall. However, for profiles measured with the Pitot tube, a slight ‘kick-up’ from the logarithmic law was observed near the buffer region, whereas the mean velocity profiles measured with a normal hot wire did not exhibit this deviation from the logarithmic law. As the layers approached equilibrium, the mean velocity profiles were found to approach the pure wall profile and for the highest level of acceleration Π was very close to zero, where Π is the Coles wake factor. This supports the proposition of Coles (1957), that the equilibrium sink flow corresponds to pure wall flow. Particular interest was also given to the evolutionary stages of the boundary layers, in order to test and further develop the closure hypothesis of Perry, Marusic & Li (1994). Improved quantitative agreement with the experimental results was found after slight modification of their original closure equation.

LDV Measurements of the Flow Field in the Nozzle Region of a Confined Double Annular Burner

2001 ◽  
Vol 123 (2) ◽  
pp. 228-236 ◽  
Author(s):  
Francois Schmitt ◽  
Birinchi K. Hazarika ◽  
Charles Hirsch
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Turbulence Intensity ◽  
Meridional Plane ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Fine Grid ◽  
Contour Plots ◽  
The Mean ◽  
Grid Points

A database for the complex turbulent flow of a confined double annular burner in cold conditions is presented here. In the region close to the exit of the annular nozzles LDV measurements at 5515 grid points in the meridional plane were conducted. At each measurement position, validated data for 3000–16,000 particles were recorded, and the mean axial and radial velocities, axial and radial turbulence intensity and Reynolds stresses were computed. The resulting mean flow field is axisymmetric within an uncertainty of 2 percent. The contour plots of turbulent quantities on the fine grid, as well as the streamlines based on the mean flow field, are presented for the flow.

scholarly journals Large-eddy simulation of three-dimensional dunes in a steady, unidirectional flow. Part 1. Turbulence statistics

2013 ◽  
Vol 721 ◽  
pp. 454-483 ◽  
Author(s):  
Mohammad Omidyeganeh ◽  
Ugo Piomelli
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Wall Stress ◽  
Two Dimensional ◽  
Streamwise Vortices ◽  
Mean Flow ◽  
Form Drag ◽  
Separated Shear Layer ◽  
Large Eddy ◽  
The Mean

AbstractWe performed large-eddy simulations of flow over a series of three-dimensional dunes at laboratory scale (Reynolds number based on the average channel depth and streamwise velocity was 18 900) using the Lagrangian dynamic eddy-viscosity subgrid-scale model. The bedform three-dimensionality was imposed by shifting a standard two-dimensional dune shape in the streamwise direction according to a sine wave. The statistics of the flow are discussed in 10 cases with in-phase and staggered crestlines, different deformation amplitudes and wavelengths. The results are validated qualitatively against experiments. The three-dimensional separation of flow at the crestline alters the distribution of wall pressure, which in turn may cause secondary flow across the stream, which directs low-momentum fluid, near the bed, toward the lobe (the most downstream point on the crestline) and high-momentum fluid, near the top surface, toward the saddle (the most upstream point on the crestline). The mean flow is characterized by a pair of counter-rotating streamwise vortices, with core radius of the order of the flow depth. However, for wavelengths smaller than the flow depth, the secondary flow exists only near the bed and the mean flow away from the bed resembles the two-dimensional case. Staggering the crestlines alters the secondary motion; the fastest flow occurs between the lobe and the saddle planes, and two pairs of streamwise vortices appear (a strong one, centred about the lobe, and a weaker one, coming from the previous dune, centred around the saddle). The distribution of the wall stress and the focal points of separation and attachment on the bed are discussed. The sensitivity of the average reattachment length, depends on the induced secondary flow, the streamwise and spanwise components of the channel resistance (the skin friction and the form drag), and the contribution of the form drag to the total resistance are also studied. Three-dimensionality of the bed increases the drag in the channel; the form drag contributes more than in the two-dimensional case to the resistance, except for the staggered-crest case. Turbulent-kinetic energy is increased in the separated shear layer by the introduction of three-dimensionality, but its value normalized by the plane-averaged wall stress is lower than in the corresponding two-dimensional dunes. The upward flow on the stoss side and higher deceleration of flow on the lee side over the lobe plane lift and broaden the separated shear layer, respectively, affecting the turbulent kinetic energy.

Experimental Investigation of a Turbulent Flow in the Vicinity of an Appendage Mounted on a Flat Plate

1991 ◽  
Vol 113 (4) ◽  
pp. 635-642 ◽  
Author(s):  
P. Merati ◽  
H. M. McMahon ◽  
K. M. Yoo
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Flat Plate ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Leading Edge ◽  
Significant Degree ◽  
Major Effect ◽  
Turbulent Shear ◽  
Mean Flow

Experimental measurements were carried out in an incompressible three-dimensional turbulent shear layer in the vicinity of an appendage mounted perpendicular to a flat plate. The thickness of the turbulent boundary layer as it approached the appendage leading edge was 76 mm or 1.07 times the maximum thickness of the appendage. As the oncoming boundary layer passed around the appendage, a strong secondary flow was formed which was dominated by a horseshoe root vortex. This secondary flow had a major effect in redistributing both the mean flow and turbulence quantities throughout the shear layer, and this effect persisted to a significant degree up to at least three chord lengths downstream of the appendage leading edge.

Sign in / Sign up

Export Citation Format

Share Document