Relative Flow and Turbulence Measurements Downstream of a Backward Centrifugal Impeller

1993 ◽  
Vol 115 (3) ◽  
pp. 543-551 ◽  
Author(s):  
M. Ubaldi ◽  
P. Zunino ◽  
A. Cattanei
Keyword(s):  
Secondary Flow ◽  
Reynolds Stress ◽  
Total Pressure ◽  
Centrifugal Impeller ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Average Technique ◽  
Flow Activity ◽  
Relative Flow

The paper presents the results of an experimental investigation on the three-dimensional relative flow at the exit of the backward bladed centrifugal impeller of the high-pressure stage of a two-stage biregulating pump-turbine model, operating at the pump nominal point. Mean velocity, Reynolds stress tensor, and total pressure of the relative flow have been measured with stationary hot-wire probes and fast response miniature pressure transducers, by means of a phase-locked ensemble-average technique. The results, shown in terms of secondary vector plots and contours of mean flow characteristics and Reynolds stress components, give a detailed picture of the flow kinematic structure and of the complex relative total pressure loss and turbulence distributions. In spite of strongly backswept blades, the flow leaving the impeller presents a jet and wake structure and an intense secondary flow activity. Large relative total pressure losses affect the wake and the region where secondary vortices interact. The turbulence data analysis provides information about the effects of the impeller rotation on the turbulence structure and about the mechanisms of the flow mixing process and of the secondary flow decay downstream of the impeller.

scholarly journals Relative Flow and Turbulence Measurements Downstream of a Backward Centrifugal Impeller

1992 ◽  
Author(s):  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Andrea Cattanei
Keyword(s):  
Secondary Flow ◽  
Reynolds Stress ◽  
Total Pressure ◽  
Centrifugal Impeller ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Average Technique ◽  
Flow Activity ◽  
Relative Flow

The paper presents the results of an experimental investigation on the three-dimensional relative flow at the exit of the backward bladed centrifugal impeller of the high pressure stage of a two stage biregulating pump-turbine model, operating at the pump nominal point. Mean velocity, Reynolds stress tensor and total pressure of the relative flow have been measured with stationary hot wire probes and fast response miniature pressure transducers, by means of a phase locked ensemble average technique. The results, shown in terms of secondary vector plots and contours of mean flow characteristics and Reynolds stress components, give a detailed picture of the flow kinematic structure and of the complex relative total pressure loss and turbulence distributions. In spite of strongly backswept blades, the flow leaving the impeller presents a jet and wake structure and an intense secondary flow activity. Large relative total pressure losses affect the wake and the region where secondary vortices interact. The turbulence data analysis provides information about the effects of the impeller rotation on the turbulence structure and about the mechanisms of the flow mixing process and of the secondary flow decay downstream of the impeller.

scholarly journals The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct

1994 ◽  
Author(s):  
K. M. Britchford ◽  
J. F. Carrotte ◽  
S. J. Stevens ◽  
J. J. McGuirk
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Anemometry ◽  
Reynolds Shear Stress ◽  
Turbulence Models ◽  
Test Facility ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Curvature Effects ◽  
The Mean

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.

Unsteady Flow Phenomena in Rotating Centrifugal Impeller Passages

1970 ◽  
Vol 92 (1) ◽  
pp. 65-71 ◽  
Author(s):  
E. Lennemann ◽  
J. H. G. Howard
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Centrifugal Impeller ◽  
Bubble Flow ◽  
Hydrogen Bubble ◽  
Visualization Technique ◽  
Rotating Systems ◽  
Flow Phenomena ◽  
Relative Flow ◽  
Zero Flow

The phenomena of unsteady relative flow observed in a centrifugal impeller passage running at part capacity and zero flow are discussed. The mechanisms of passage stall for a shrouded and unshrouded impeller are investigated and a qualitative correlation is developed for the influence of secondary flow and inducer flow on the passage stall. The hydrogen bubble flow visualization technique is extended to higher velocities and rotating systems and provides the method for obtaining the experimental results.

scholarly journals Effect of the Flame Dome Depth and Improvement of the Pressure Loss in the Dump Diffuser

1998 ◽  
Author(s):  
Shinji Honami ◽  
Wataru Tsuboi ◽  
Takaaki Shizawa
Keyword(s):  
Velocity Profile ◽  
Reynolds Stress ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Flow Behavior ◽  
Sudden Expansion ◽  
Mean Velocity ◽  
The Mean ◽  
Stress Profiles

This paper presents the effect of flame dome depth on the total pressure performance and flow behavior in a sudden expansion region of the combustor diffuser without flow entering the dome head. The mean velocity and turbulent Reynolds stress profiles in the sudden expansion region were measured by a Laser Doppler Velocitmetry (LDV) system. The experiments show that total pressure loss is increased, when flame dome depth is increased. Installation of an inclined combuster wall in the sudden expansion region is suggested from the viewpoint of a control of the reattaching flow. The inclined combustor wall is found to be effective in improvement of the diffuser performance. Better characteristics of the flow rate distribution into the branched channels are obtained in the inclined wall configuration, even if the distorted velocity profile is provided at the diffuser inlet.

A vortex-street model of the flow in the similarity region of a two-dimensional free turbulent jet

1982 ◽  
Vol 123 ◽  
pp. 523-535 ◽  
Author(s):  
J. W. Oler ◽  
V. W. Goldschmidt
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Turbulent Jet ◽  
Vortex Street ◽  
Two Dimensional ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Core ◽  
The Mean ◽  
Similarity Relationships

The mean-velocity profiles and entrainment rates in the similarity region of a two-dimensional jet are generated by a simple superposition of Rankine vortices arranged to represent a vortex street. The spacings between the vortex centres, their two-dimensional offsets from the centreline, as well as the core radii and circulation strengths, are all governed by similarity relationships and based upon experimental data.Major details of the mean flow field such as the axial and lateral mean-velocity components and the magnitude of the Reynolds stress are properly determined by the model. The sign of the Reynolds stress is, however, not properly predicted.

scholarly journals Effects of Tip Leakage on Relative Flow and Reynolds Stress at Midpassage of a Centrifugal Impeller.

1997 ◽  
Vol 63 (609) ◽  
pp. 1649-1654 ◽  
Author(s):  
Hiroyuki MIYAMOTO ◽  
Satoshi MATSUMOTO ◽  
Itsuro HONDA ◽  
Hideki OHBA
Keyword(s):  
Reynolds Stress ◽  
Centrifugal Impeller ◽  
Tip Leakage ◽  
Relative Flow

Flow at the Centrifugal Pump Impeller Exit With Circumferential Distortion of the Outlet Static Pressure

2004 ◽  
Vol 126 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Soon-Sam Hong ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Total Pressure ◽  
Static Pressure ◽  
Mean Flow ◽  
Simple Method ◽  
Local Flow ◽  
Flow Angle ◽  
Flow Parameters ◽  
Relative Flow

The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller exit flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser exit. The flow field was measured at the impeller exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean flow parameters plotted against the local flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller exit with the relative flow angle or total pressure assumed. Good result was obtained when the relative flow angle was assumed to vary quasi-steadily, not constant with the local flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller exit flow with downstream blockage in two-step sequence: the first step deals with the diffuser alone to obtain static pressure distribution at the diffuser inlet, while the second step deals with the impeller alone to obtain velocity components distribution at the impeller exit.

An investigation of turbulent plane Couette flow at low Reynolds numbers

1995 ◽  
Vol 286 ◽  
pp. 291-325 ◽  
Author(s):  
Knut H. Bech ◽  
Nils Tillmark ◽  
P. Henrik Alfredsson ◽  
Helge I. Andersson
Keyword(s):  
Couette Flow ◽  
Reynolds Stress ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Turbulence Structure ◽  
Plane Couette Flow ◽  
Mean Flow ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Near Wall

The turbulent structure in plane Couette flow at low Reynolds numbers is studied using data obtained both from numerical simulation and physical experiments. It is shown that the near-wall turbulence structure is quite similar to what has earlier been found in plane Poiseuille flow; however, there are also some large differences especially regarding Reynolds stress production. The commonly held view that the maximum in Reynolds stress close to the wall in Poiseuille and boundary layer flows is due to the turbulence-generating events must be modified as plane Couette flow does not exhibit such a maximum, although the near-wall coherent structures are quite similar. For two-dimensional mean flow, turbulence production occurs only for the streamwise fluctuations, and the present study shows the importance of the pressure—strain redistribution in connection with the near-wall coherent events.

The Influence of Inlet Conditions on the Performance of Annular Diffusers

1980 ◽  
Vol 102 (3) ◽  
pp. 357-363 ◽  
Author(s):  
S. J. Stevens ◽  
G. J. Williams
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Turbulence Structure ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Outlet Flow ◽  
Inlet Conditions ◽  
Uniform Diameter

Low speed tests have been carried out to investigate the performance and mechanism of flow in two annular diffusers having center bodies of uniform diameter and conically diverging outer walls. In the first part of the investigation the diffusers were tested over a range of naturally developed inlet velocity profiles ranging from near-uniform to fully developed flow. Information is presented concerning the pressure recovery, total pressure loss, and characteristics of the outlet flow. Measurements have also been made of the mean velocity profile and turbulence structure at a number of stations along the length of the diffusers. The second part of the test program was devoted to studying the effects of increased inlet turbulence. The results show a marked improvement in the stability of the outlet flow and gains in pressure recovery, up to a maximum of 20 percent, with only small increases in total pressure loss.

Calculations of a Curved-Pipe Flow Using Reynolds Stress Closure

1991 ◽  
Vol 205 (4) ◽  
pp. 231-244 ◽  
Author(s):  
Y G Lai ◽  
R M C So ◽  
M Anwer ◽  
B C Hwang
Keyword(s):  
Secondary Flow ◽  
Reynolds Stress ◽  
Pipe Flow ◽  
Wall Region ◽  
Sudden Increase ◽  
Normal Stresses ◽  
Mean Flow ◽  
Flow Measurements ◽  
Curved Pipe ◽  
Near Wall

It has been observed that as a fully developed turbulent flow enters a curved bend the anisotropy of the normal stresses near the outer bend (furthest from the centre of the bend curvature) increases. According to the arguments of vorticity generation, a sudden increase in the anisotropy of the normal stresses may lead to the formation of a secondary flow of the second kind. If this secondary motion is to be calculated, then a near-wall Reynolds stress closure that can mimic the anisotropic turbulence behaviour near a wall has to be used. This study presents the results of just such an attempt. In addition, two high Reynolds number closures assuming wall functions in the near-wall region are tested for their ability to replicate the behaviour of the normal stresses in a curved-pipe flow. These two closures differ in their modelling of the pressure-strain terms. Consequently, the effects of near-wall and pressure-strain modelling on curved-pipe flow calculations can be examined. Comparisons are also made with recent curved-pipe flow measurements. The results show that pressure-strain modelling alone is not sufficient to predict the rapid rise of the anisotropy of the normal stresses near the outer bend, and hence the formation of the secondary flow of the second kind. Overall, the near-wall Reynolds stress closure gives a more accurate prediction of the measured mean flow and turbulence statistics, and a realistic calculation of the secondary flow of the second kind near the outer bend.

Sign in / Sign up

Export Citation Format

Share Document