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 Self-consistent triple decomposition of the turbulent flow over a backward-facing step under finite amplitude harmonic forcing

2019 ◽  
Vol 475 (2225) ◽  
pp. 20190018
Author(s):  
E. Yim ◽  
P. Meliga ◽  
F. Gallaire
Keyword(s):  
Turbulent Flow ◽  
Finite Amplitude ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Backward Facing Step ◽  
Eddy Viscosity Model ◽  
Coherent Interaction ◽  
Self Consistent ◽  
The Mean

We investigate the saturation of harmonically forced disturbances in the turbulent flow over a backward-facing step subjected to a finite amplitude forcing. The analysis relies on a triple decomposition of the unsteady flow into mean, coherent and incoherent components. The coherent–incoherent interaction is lumped into a Reynolds averaged Navier–Stokes (RANS) eddy viscosity model, and the mean–coherent interaction is analysed via a semi-linear resolvent analysis building on the laminar approach by Mantič-Lugo & Gallaire (2016 J. Fluid Mech. 793 , 777–797. ( doi:10.1017/jfm.2016.109 )). This provides a self-consistent modelling of the interaction between all three components, in the sense that the coherent perturbation structures selected by the resolvent analysis are those whose Reynolds stresses force the mean flow in such a way that the mean flow generates exactly the aforementioned perturbations, while also accounting for the effect of the incoherent scale. The model does not require any input from numerical or experimental data, and accurately predicts the saturation of the forced coherent disturbances, as established from comparison to time-averages of unsteady RANS simulation data.

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.

Measurement of the Reynolds stresses and the mean-flow field in a three-dimensional pressure-driven boundary layer

1982 ◽  
Vol 119 ◽  
pp. 121-153 ◽  
Author(s):  
Udo R. Müller
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Flow Field ◽  
Three Dimensional ◽  
Turbulent Shear ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Acceleration ◽  
The Mean

An experimental study of a steady, incompressible, three-dimensional turbulent boundary layer approaching separation is reported. The flow field external to the boundary layer was deflected laterally by turning vanes so that streamwise flow deceleration occurred simultaneous with cross-flow acceleration. At 21 stations profiles of the mean-velocity components and of the six Reynolds stresses were measured with single- and X-hot-wire probes, which were rotatable around their longitudinal axes. The calibration of the hot wires with respect to magnitude and direction of the velocity vector as well as the method of evaluating the Reynolds stresses from the measured data are described in a separate paper (Müller 1982, hereinafter referred to as II). At each measuring station the wall shear stress was inferred from a Preston-tube measurement as well as from a Clauser chart. With the measured profiles of the mean velocities and of the Reynolds stresses several assumptions used for turbulence modelling were checked for their validity in this flow. For example, eddy viscosities for both tangential directions and the corresponding mixing lengths as well as the ratio of resultant turbulent shear stress to turbulent kinetic energy were derived from the data.

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.

PIV Investigation of Turbulent Flow Over a Wavy-Wall in a Horizontal Channel

2016 ◽  
Author(s):  
Vinicius Martins Segunda ◽  
Mark Tachie ◽  
Scott Ormiston
Keyword(s):  
Turbulent Flow ◽  
Reynolds Shear Stress ◽  
Flow Characteristics ◽  
Wavy Wall ◽  
Mean Flow ◽  
Particle Image Velocimetry Technique ◽  
Turbulent Characteristics ◽  
Developing Region ◽  
Contour Plots ◽  
The Mean

Experimental investigation of turbulent flow in a channel with flat upper wall and wavy lower wall using a particle image velocimetry technique is presented. The mean flow and turbulent characteristics in both the developing region and fully periodic region over the wavy wall were examined. It was observed that the flow characteristics become fully periodic after the eighth wave. The results also showed that the separation and reattachment points within the developing region and fully periodic region are similar. Detailed investigation of the flow field in the fully periodic region was examined using contour plots and one-dimensional profiles of the mean velocities, mean spanwise vorticity, streamwise and wall-normal turbulence intensities and Reynolds shear stress.

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.

The Control Method with Energy Saving of the Inflow Turbulence for Router Cooling Fan

2014 ◽  
Vol 886 ◽  
pp. 394-397 ◽  
Author(s):  
Ying Bo Xu ◽  
Xiao Dong Li
Keyword(s):  
Flow Field ◽  
Energy Saving ◽  
Turbulence Intensity ◽  
Control Method ◽  
Hot Wire ◽  
Mean Flow ◽  
Cooling Fan ◽  
Inflow Turbulence ◽  
The Mean

In this paper, the characteristics of the inflow turbulence intensity of a router cooling fan are studied experimentally. Screens with different parameters are designed to control the inflow turbulence intensity. The flow field is measured by hot-wire anemometer. The results show that the inflow turbulence intensity is closely connected with the parameters of the control screens. The inflow turbulence intensity can be significantly reduced when the screen with small meshes is used, while the mean flow is barely affected by the screen.

The Flow Pattern in a Scalene Triangular Duct Having Two Rounded Corners

1985 ◽  
Vol 107 (4) ◽  
pp. 455-459 ◽  
Author(s):  
N. T. Obot ◽  
K. Adu-Wusu
Keyword(s):  
Pressure Drop ◽  
Laminar Flow ◽  
Flow Field ◽  
Turbulent Flow ◽  
Flow Pattern ◽  
Friction Factor ◽  
Mean Flow ◽  
Mean Velocity ◽  
Pipe Line ◽  
The Mean

Experiments were carried out to determine the pressure drop characteristics and mean velocity distributions in a scalene triangualr duct having two rounded corners. The present data for friction factor are adequately represented by the circular pipe line for laminar flow, but fall below the latter for turbulent flow. The mean flow field is highly asymmetric, the degree of asymmetry being more accentuated along lines parallel to the altitude than parallel to the base.

Turbulent flow past a porous plate

1976 ◽  
Vol 73 (3) ◽  
pp. 565-591 ◽  
Author(s):  
J. M. R. Graham
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Turbulent Flow ◽  
Porous Plate ◽  
Lattice Structures ◽  
Extended Version ◽  
Mean Flow ◽  
Flow Past ◽  
Flow Through ◽  
The Mean

The method of Vickery for calculating the drag of plane lattice structures normal to a turbulent stream is extended to cases of increased solidity. The analysis incorporates an extended version of Taylor's theory for the flow through a porous plate, and a simplified version of Hunt's analysis of the distortion of a turbulent flow by the mean flow field of a body. Some comparisons are made with experimental data.

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

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