scholarly journals LDV Measurement of Confined Parallel Jet Mixing

2000 ◽  
Vol 123 (3) ◽  
pp. 567-573 ◽  
Author(s):  
Robert F. Kunz ◽  
Stephen W. D’Amico ◽  
Peter F. Vassallo ◽  
Michael A. Zaccaria
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Velocimetry ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Mixing Process ◽  
Mean Velocity ◽  
Jet Mixing ◽  
Transverse Diffusion ◽  
Stress Components ◽  
Ldv Measurement

Laser Doppler Velocimetry (LDV) measurements were taken in a confinement, bounded by two parallel walls, into which issues a row of parallel jets. Two-component measurements were taken of two mean velocity components and three Reynolds stress components. As observed in isolated three-dimensional wall bounded jets, the transverse diffusion of the jets is quite large. The data indicate that this rapid mixing process is due to strong secondary flows, transport of large inlet intensities, and Reynolds stress anisotropy effects.

Reynolds-Stress Modeling of Three-Dimensional Secondary Flows With Emphasis on Turbulent Diffusion Closure

2007 ◽  
Vol 74 (6) ◽  
pp. 1142-1156 ◽  
Author(s):  
I. Vallet
Keyword(s):  
Reynolds Stress ◽  
Turbulent Diffusion ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Reynolds Stress Model ◽  
Secondary Flows ◽  
Velocity Correlation ◽  
Mean Velocity ◽  
Diffusion Term ◽  
Spatial Gradients

The purpose of this paper is to assess the importance of the explicit dependence of turbulent diffusion on the gradients of mean-velocity modeling in second moment closures on three-dimensional (3D) detached and secondary flows prediction. Following recent theoretical work of Younis, Gatski, and Speziale, 2000, [Proc. Royal Society Lon. A, 456, pp. 909–920], we propose a triple-velocity correlation model, including the effects of the spatial gradients of mean velocity. A model for both the slow and rapid parts of the pressure-diffusion term was also developed and added to a wall-normal-free Reynolds-stress model. The present model is validated against 3D detached and secondary flows. Further developments, especially on the echo terms (which should appear in the formulation of pressure-velocity correlation), are discussed.

Development of a Two-Dimensional Turbulent Wake in a Curved Channel With a Positive Streamwise Pressure Gradient

1996 ◽  
Vol 118 (2) ◽  
pp. 292-299 ◽  
Author(s):  
J. John ◽  
M. T. Schobeiri
Keyword(s):  
Pressure Gradient ◽  
Reynolds Stress ◽  
Gaussian Function ◽  
Two Dimensional ◽  
Curved Channel ◽  
Mean Velocity ◽  
Velocity Defect ◽  
Curved Channels ◽  
Stress Components ◽  
Streamwise Pressure Gradient

The development of turbomachinery wake flows is greatly influenced by streamline curvature and streamwise pressure gradient. This paper is part of a comprehensive experimental and theoretical study on the development of the steady and periodic unsteady turbulent wakes in curved channels at different streamwise pressure gradients. This paper reports on the experimental investigation of the two-dimensional wake behind a stationary circular cylinder in a curved channel at positive streamwise pressure gradient. Measurements of mean velocity and Reynolds stress components are carried out using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake center line and are presented in similarity coordinates. The results show strong asymmetry in velocity and Reynolds stress components. The Reynolds stress components have higher values at the inner half of the wake than at the outer half of the wake. However, the mean velocity defect profiles in similarity coordinates are almost symmetric and follow the same Gaussian function for the straight wake data. A comparison with the wake development in a curved channel at zero streamwise pressure gradient suggests the decay rate of velocity defect is slower and the growth of wake width is faster for a positive streamwise pressure gradient.

scholarly journals Development of Two-Dimensional Turbulent Wakes in a Curved Channel at Positive Streamwise Pressure Gradient

1994 ◽  
Author(s):  
J. John ◽  
M. T. Schobeiri
Keyword(s):  
Pressure Gradient ◽  
Reynolds Stress ◽  
Gaussian Function ◽  
Two Dimensional ◽  
Curved Channel ◽  
Mean Velocity ◽  
Velocity Defect ◽  
Turbulent Wakes ◽  
Stress Components ◽  
Streamwise Pressure Gradient

The development of turbomachinery wake flows are greatly influenced by streamline curvature and streamwise pressure gradient. This paper is a part of a comprehensive experimental and theoretical study on the development of the steady and the periodic unsteady turbulent wakes in curved channels at different streamwise pressure gradients. The experimental investigation of the two-dimensional wake behind a stationary circular cylinder in a curved channel at positive streamwise pressure gradient is reported in this paper. Measurements of mean velocity and Reynolds stress components are carried out using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake center line and are presented in similarity coordinates. The results indicates strong asymmetry in velocity and Reynolds stress components. The Reynolds stress components have higher values at the inner half of the wake than at the outer half of the wake. However, the mean velocity defect profiles in similarity coordinates is almost symmetric and follows the same Gaussian function for the straight wake data. A comparison with the wake development in a curved channel at zero streamwise pressure gradient suggests that the decay rate of velocity defect is slower and the growth of wake width is faster in the case of positive streamwise pressure gradient.

Effects of Guide-Vane Number in a Three-Dimensional 60-Deg Curved Side-Dump Combustor Inlet

2000 ◽  
Vol 123 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Tong-Miin Liou ◽  
Hsin-Li Lee ◽  
Chin-Chun Liao
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Laser Doppler Velocimetry ◽  
Guide Vane ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Mean Velocity ◽  
Guide Vanes ◽  
Aspect Ratios ◽  
The One

Three-dimensional flowfields in a 60-deg curved combustor inlet duct of rectangular cross-section with and without guide vanes were measured using Laser-Doppler velocimetry for the longitudinal, radial, and spanwise velocity components. The Reynolds number based on the bulk mean velocity and hydraulic diameter was 2.53×104. The main parameters examined were the guide-vane number and Reynolds number. The results show that to completely eliminate flow separation in the curved combustor inlet three guide vanes should be installed. The critical Reynolds number for the absence of the flow separation is found to decrease with increasing product of radius and aspect ratios. In addition, it is found that in most regions the maximum radial mean velocity, difference between radial and spanwise normal stress, and the turbulent kinetic energy decrease with increasing guide-vane number. A rationale for the absence of flow separation in the one-vane case predicted by previous researchers is also provided.

Reynolds stress distribution and turbulence generated secondary flow in the turbulent three-dimensional wall jet

2016 ◽  
Vol 800 ◽  
pp. 613-644 ◽  
Author(s):  
L. Namgyal ◽  
J. W. Hall
Keyword(s):  
Secondary Flow ◽  
Reynolds Stress ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Half Width ◽  
Stereoscopic Particle Image Velocimetry ◽  
Wall Jet ◽  
Normal Stresses ◽  
Reynolds Stresses

The lateral half-width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half-width normal to the wall. Although the reason for this behaviour is not fully understood, it is caused by mean secondary flows that develop in the jet due to the presence of the wall. The origin of the secondary flow has been associated previously with both vorticity reorientation and also gradients in the Reynolds stresses, although this has not been directly quantified as yet. The present investigation focuses on a wall jet formed using a circular contoured nozzle with exit Reynolds number of 250 000. Stereoscopic particle image velocimetry measurements are used herein to measure the three-component velocity, thereby allowing access to the full Reynolds stress tensor that contributes to the secondary flow in a turbulent three-dimensional wall jet. Throughout the jet, the Reynolds normal stress ($\overline{u^{2}}$) makes the largest contribution to the Reynolds stress field whereas Reynolds shear stress ($\overline{vw}$) is found to be negligible when compared with other stresses. In particular, the differences in the Reynolds normal stresses ($\overline{v^{2}}-\overline{w^{2}}$) are found to be significantly larger than $\overline{vw}$; these terms are important for the generation of turbulence secondary flow in the wall jet. Above all, the differences in the Reynolds normal stresses are oriented to reinforce the near-wall streamwise vorticity, and thus contribute to the large lateral growth of this flow. The contours of the turbulent kinetic budget indicate that the turbulent energy budget obtained on the jet centreline is different from that obtained off of the jet centreline.

scholarly journals Unsteady Three-Dimensional Flow Behavior due to Rotor-Stator Interaction in an Axial-Flow Turbine

1993 ◽  
Author(s):  
A. Yamamoto ◽  
F. Mimura ◽  
J. Tominaga ◽  
S. Tomihisa ◽  
E. Outa ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Three Dimensional ◽  
Axial Flow ◽  
Secondary Flows ◽  
Mixing Process ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Tip Leakage ◽  
Second Stage ◽  
Rotor Stator Interaction

Detailed unsteady flow surveys were conducted before, within and after the second-stage stator passage of a 1.5-stage axial flow turbine by using a single slanted hot-wire anemometry. Among the results reported in the present paper, of particular interest are the behavior of the rotor wakes and the rotor free-streams within the stator passage, and the spacially three-dimensional and time-dependent convection or mixing process between lower- and higher- energy fluids. Effects of the rotor-stator interaction causing unsteady secondary flows and tip-leakage flow are also discussed.

Three-Dimensional Laser Anemometer Measurements in an Annular Seal

1991 ◽  
Vol 113 (3) ◽  
pp. 421-427 ◽  
Author(s):  
G. L. Morrison ◽  
M. C. Johnson ◽  
G. B. Tatterson
Keyword(s):  
Reynolds Stress ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Mean Velocity ◽  
Anisotropic Turbulence ◽  
Laser Anemometer ◽  
Annular Seal ◽  
The Mean ◽  
Tensor Distributions ◽  
Anemometer System

The flow field inside an annular seal with a 1.27 mm clearance is investigated using a 3-D laser Doppler anemometer system. Through the use of this system, the mean velocity vector and the entire Reynolds stress tensor distributions are measured for the entire length of the seal (37.3 mm). The seal is operated at a Reynolds number of 18,600 and a Taylor number of 4500. The annular seal is found to produce anisotropic turbulence since the Reynolds stress measurements show the flow entering the seal with isotropic turbulence but exiting the seal with anisotropic turbulence.

Three Component LDV Velocity Measurements in a Can Type Research Combustor for CFD Validation: Part 1 — Isothermal

1992 ◽  
Author(s):  
Saad A. Ahmed ◽  
Alan Rose ◽  
Abdollah S. Nejad
Keyword(s):  
Reynolds Stress ◽  
Early Stage ◽  
Primary Objective ◽  
Velocity Measurements ◽  
Radial Velocity Component ◽  
Cfd Validation ◽  
Mean Velocity ◽  
Numerical Predictions ◽  
Stress Components ◽  
Modelling Approach

A two-component fibre optic LDV system has been employed to measure three mean velocity components and five Reynolds Stress components in a confined, isothermal strongly swirling flowfield. The primary objective is to provide complete benchmark data for comparisons with numerical predictions based on practical models for turbulent swirling flows and thereby guide the development of such models. Results of initial modelling work are presented and even at this early stage in the programme, the superiority of the Reynolds Stress modelling approach is clearly illustrated through comparisons with the results from experiment and a typical k–ε model. Measurements show the radial velocity component (close to the swirler exit) to be of the same magnitude as the axial and swirl components. Velocity measurements obtained close to the combustor wall should be treated with caution as these were most affected by signal noise as a result of internal wall reflections.

Confined Jet Mixing for Nonseparating Conditions

1971 ◽  
Vol 93 (3) ◽  
pp. 333-347 ◽  
Author(s):  
E. Razinsky ◽  
J. A. Brighton
Keyword(s):  
Reynolds Stress ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Lower Velocity ◽  
Jet Mixing ◽  
Air Jet ◽  
Air Stream ◽  
Constant Diameter ◽  
Diameter Pipe ◽  
The Mean

The mixing of an air jet with a lower-velocity air stream is described. The mixing takes place in a constant diameter pipe, and the flow is investigated from the inlet where the jet and secondary velocities are uniform (but different) to a location downstream where the flow is fully developed. Measurements are made of (1) the wall static pressure, (2) the mean velocity, (3) the turbulence velocities and Reynolds stress throughout the flow field for different velocity ratios and diameter ratios. This work differs from previous investigations in that a wider range of flow conditions is considered, i.e., different diameter and velocity ratios in addition to the flow in the latter stages of mixing. Also, the turbulence velocities and Reynolds stress as determined throughout the flow are described.

Sign in / Sign up

Export Citation Format

Share Document