Stereo-PIV Measurements of Turbulent Swirling Flow Inside a Pipe

2020 ◽  
Author(s):  
Ayesha Almheiri ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Saqib Salam ◽  
Afshin Goharzadeh
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Tangential Velocity ◽  
Circular Disk ◽  
Pipe Diameter ◽  
Working Fluid ◽  
Complex Flow ◽  
Mean Velocity ◽  
Radial Profiles ◽  
The Mean

Abstract Stereo-PIV is used to map turbulent strongly swirling flow inside a pipe connected to a closed recirculating system with a transparent test section of 0.6 m in length and a pipe diameter of 0.041 m. The Perspex pipe was immersed inside a water trough to reduce the effects of refraction. The working fluid was water and the Reynolds number based on the bulk average velocity inside the pipe and pipe diameter was equal to 14,450. The turbulent flow proceeds in the downstream direction and interacts with a circular disk. The measurements include instantaneous velocity vector fields and radial profiles of the mean axial, radial and tangential components of the velocity in the regions between the swirler exit and circular disk and around this later. The results for mean axial velocity show a symmetric behavior with a minimum reverse flow velocity along the centerline. As the flow developed along the pipe’s length, the intensity of the reversed flow was reduced and the intensity of the swirl decays. The mean tangential velocity exhibits a Rankine-vortex distribution and reached its maximum around half of the pipe’s radius. As the flow approaches the disk, the flow reaches stagnation and a complex flow pattern of vortices is formed. The PIV results are contrasted with LDV measurements of mean axial and tangential velocity. Good agreement is shown over the mean velocity profiles.

Experiments on Turbulent Air-Water Swirling Flow in a Pipe With a Circular Disk

2019 ◽  
Author(s):  
Zhang Tianxing ◽  
Ayesha Almheiri ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Saqib Salam
Keyword(s):  
High Speed ◽  
Bluff Body ◽  
Swirling Flow ◽  
Liquid Velocity ◽  
Reverse Flow ◽  
Circular Disk ◽  
Internal Diameter ◽  
High Speed Photography ◽  
Two Phase ◽  
Radial Profiles

Abstract This paper presents an experimental study conducted on turbulent single and two-phase swirling flow in a circular pipe with a bluff body. Laser Doppler Velocimetry (LDV) was used to measure liquid velocity radial profiles. The measurements were performed in a closed water-air loop system with a horizontal test section of length 610 mm and 41 mm internal diameter. The measurement campaign was performed at different axial locations to document the flow field without and with the presence of an air core respectively. The measurements were conducted with water flow rates which corresponded to Reynolds numbers based on pipe diameter and average liquid velocity of 14,500 and 19,450 for single phase and liquid-gas swirling flow, respectively. Analysis of the results reveals a more noticeable reverse flow along the whole pipe intensifying rather than being dampened as expected due to the swirl decay. High-speed photography shows that at a GLR = 0.3% the gas core does not touch the bluff body but breaks down just ahead of the disk surface.

Turbulence measurements in axisymmetric jets of air and helium. Part 2. Helium jet

1993 ◽  
Vol 246 ◽  
pp. 225-247 ◽  
Author(s):  
N. R. Panchapakesan ◽  
J. L. Lumley
Keyword(s):  
Density Ratio ◽  
Effective Diameter ◽  
Mean Velocity ◽  
Velocity Fluctuations ◽  
Air Jet ◽  
Plume Region ◽  
Turbulent Schmidt Number ◽  
Radial Profiles ◽  
The Mean ◽  
Mean Concentration

A turbulent round jet of helium was studied experimentally using a composite probe consisting of an interference probe of the Way–Libby type and an × -probe. Simultaneous measurements of two velocity components and helium mass fraction concentration were made in the x/d range 50–120. These measurements are compared with measurements in an air jet of the same momentum flux reported in Part 1. The jet discharge Froude number was 14000 and the measurement range was in the intermediate region between the non-buoyant jet region and the plume region. The measurements are consistent with earlier studies on helium jets. The mass flux of helium across the jet is within ±10% of the nozzle input. The mean velocity field along the axis of the jet is consistent with the scaling expressed by the effective diameter but the mean concentration decay constant exhibits a density-ratio dependence. The radial profiles of mean velocity and mean concentration agree with earlier measurements, with the half-widths indicating a turbulent Schmidt number of 0.7. Significantly higher intensities of axial velocity fluctuations are observed in comparison with the air jet, while the intensities of radial and azimuthal velocity fluctuations are virtually identical with the air jet when scaled with the half-widths. Approximate budgets for the turbulent kinetic energy, scalar variance and scalar fluxes are presented. The ratio of mechanical to scalar timescales is found to be close to 1.5 across most of the jet. Current models for triple moments involving scalar fluctuations are compared with measurements. As was observed with the velocity triple moments in Part 1, the performance of the Full model that includes all terms except advection was found to be very good in the fully turbulent region of the jet.

Wechselwirkung kondensierter Molekularstrahlen mit festen Oberflächen

1968 ◽  
Vol 23 (2) ◽  
pp. 274-279 ◽  
Author(s):  
E. W. Becker ◽  
R. Klingelhöfer ◽  
H. Mayer
Keyword(s):  
Steel Surface ◽  
Tangential Velocity ◽  
Incident Beam ◽  
Stainless Steel Surface ◽  
Angle Of Incidence ◽  
Mean Velocity ◽  
Tangential Velocity Component ◽  
Polished Stainless Steel ◽  
The Mean ◽  
Angle Of Reflection

The reflection of a beam of nitrogen clusters from a polished stainless steel surface is investigated. The scattered flux shows a strong maximum at an angle of reflection almost 90°, independent of angle of incidence. The mean velocity of the reflected beam is about equal to the tangential velocity component of the incident beam. Measurements with increased background pressure demonstrate that the reflected beam still consists essentially of clusters.

Ultrasound Vector Flow Imaging – could be a new tool in evaluation of arteriovenous fistulas for hemodialysis?

2017 ◽  
Vol 18 (4) ◽  
pp. 284-289 ◽  
Author(s):  
Ilaria Fiorina ◽  
Maria Vittoria Raciti ◽  
Alfredo Goddi ◽  
Vito Cantisani ◽  
Chandra Bortolotto ◽  
...  
Keyword(s):  
Venous Aneurysm ◽  
Flow Imaging ◽  
Angular Deviation ◽  
Complex Flow ◽  
Mean Velocity ◽  
Ultrasound Technique ◽  
Arteriovenous Fistulas ◽  
The Mean ◽  
Vessel Walls ◽  
Ultrasound Scanner

Introduction We report the use of a new ultrasound technique to evaluate the axial and lateral components of a complex flow in the arteriovenous fistula (AVF). Vector Flow Imaging (VFI) allows to identify different components of the flow in every direction, even orthogonal to the flow streamline, represented by many single vectors. VFI could help to identify flow alterations in AVF, probably responsible for its malfunction. Methods From February to June 2016, 14 consecutive patients with upper-limb AVF were examined with a Resona 7 (Mindray, Shenzhen, China) ultrasound scanner equipped with VFI. An analysis of mean velocity, angular direction and mean number of vectors impacting the vessel wall was carried out. We also identified main flow patterns present in the arterial side, into the venous aneurysm and in correspondence of significant stenosis. Results A disturbed flow with the presence of vectors directed against the vessel walls was found in 9/14 patients (64.28%): in correspondence of the iuxta-anastomotic venous side (4/9; 44.4%), into the venous aneurysmal tracts (3/9; 33.3%) and in concomitance of stenosis (2/9; 22.2%). The mean velocity of the vectors was around 20-25 cm/s, except in presence of stenosis, where the velocities were much higher (45-50 cm/s). The vectors directed against the vessel walls presented high angle attack (from 45° to 90°, with a median angular deviation 65°). Conclusions VFI was confirmed to be an innovative and intuitive imaging technology to study the flow complexity in the arteriovenous fistulas.

Study of Flame Stability in a Step Swirl Combustor

1996 ◽  
Vol 118 (2) ◽  
pp. 308-315 ◽  
Author(s):  
M. D. Durbin ◽  
M. D. Vangsness ◽  
D. R. Ballal ◽  
V. R. Katta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Combustion Stability ◽  
Combustion Model ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Swirl Combustor ◽  
Radial Profiles

A prime requirement in the design of a modern gas turbine combustor is good combustion stability, especially near lean blowout (LBO), to ensure an adequate stability margin. For an aeroengine, combustor blow-off limits are encountered during low engine speeds at high altitudes over a range of flight Mach numbers. For an industrial combustor, requirements of ultralow NOx emissions coupled with high combustion efficiency demand operation at or close to LBO. In this investigation, a step swirl combustor (SSC) was designed to reproduce the swirling flow pattern present in the vicinity of the fuel injector located in the primary zone of a gas turbine combustor. Different flame shapes, structure, and location were observed and detailed experimental measurements and numerical computations were performed. It was found that certain combinations of outer and inner swirling air flows produce multiple attached flames, aflame with a single attached structure just above the fuel injection tube, and finally for higher inner swirl velocity, the flame lifts from the fuel tube and is stabilized by the inner recirculation zone. The observed difference in LBO between co- and counterswirl configurations is primarily a function of how the flame stabilizes, i.e., attached versus lifted. A turbulent combustion model correctly predicts the attached flame location(s), development of inner recirculation zone, a dimple-shaped flame structure, the flame lift-off height, and radial profiles of mean temperature, axial velocity, and tangential velocity at different axial locations. Finally, the significance and applications of anchored and lifted flames to combustor stability and LBO in practical gas turbine combustors are discussed.

Study of Flame Stability in a Step Swirl Combustor

1995 ◽  
Author(s):  
Mark D. Durbin ◽  
Marlin D. Vangsness ◽  
Dilip R. Ballal ◽  
Viswanath R. Katta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Combustion Stability ◽  
Combustion Model ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Swirl Combustor ◽  
Radial Profiles

A prime requirement in the design of a modem gas turbine combustor is good combustion stability, especially near lean blowout (LBO), to ensure an adequate stability margin. For an aeroengine, combustor blow-off limits are encountered during low engine speeds at high altitudes over a range of flight Mach numbers. For an industrial combustor, requirements of ultra-low NOx emissions coupled with high combustion efficiency demand operation at or close to LBO. In this investigation, a step swirl combustor (SSC) was designed to reproduce the swirling flow pattern present in the vicinity of the fuel injector located in the primary zone of a gas turbine combustor. Different flame shapes, structure and location were observed and detailed experimental measurements and numerical computations were performed. It was found that certain combinations of outer and inner swirling air flows produce multiple attached flames, a flame with a single attached structure just above the fuel injection tube, and finally for higher inner swirl velocity, the flame lifts from the fuel tube and is stabilized by the inner recirculation zone. The observed difference in LBO between co- and counter-swirl configurations is primarily a function of how the flame stabilizes i.e., attached vs. lifted. A turbulent combustion model correctly predicts the attached flame location(s), development of inner recirculation zone, a dimple-shaped flame structure, the flame lift-off height, and radial profiles of mean temperature, axial velocity, and tangential velocity at different axial locations. Finally, the significance and applications of anchored and lifted flames to combustor stability and LBO in practical gas turbine combustors are discussed.

Similarity in swirling wakes and jets

1962 ◽  
Vol 14 (2) ◽  
pp. 241-243 ◽  
Author(s):  
A. J. Reynolds
Keyword(s):  
Angular Momentum ◽  
Swirling Flow ◽  
Turbulent Wake ◽  
Linear Momentum ◽  
Length Scale ◽  
Mean Velocity ◽  
Swirl Velocity ◽  
Velocity Scale ◽  
Zero Momentum ◽  
The Mean

Both the net linear momentum and the net angular momentum of a developing swirling flow can play important parts in determining its ultimate form. To illustrate this the turbulent wake with both axial and swirl components of mean velocity is discussed, in particular for the two limiting cases of domination by linear momentum and domination by angular momentum. The dual conservation of axial and angular momentum implies that in general the mean swirl component decreases more rapidly downstream than does the defect in the mean axial velocity. Hence wakes with non-zero momentum flux ultimately have the familiar length scale $\sim Z^{\frac{1}{3}$ and velocity defect scale $\sim Z^{-\frac{2}{3}$. But in the wake of a self-propelled body the net drag is negligible and a swirl-dominated development can persist with length scale $\sim Z^{\frac{1}{4}$ and swirl velocity scale $\sim Z^{-\frac{3}{4}$.

Decaying Annular Swirl Flow With Inlet Solid Body Rotation

1976 ◽  
Vol 98 (1) ◽  
pp. 33-40 ◽  
Author(s):  
C. J. Scott ◽  
K. W. Bartelt
Keyword(s):  
Experimental Data ◽  
Angular Momentum ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Swirl Flow ◽  
Working Fluid ◽  
Pressure Probe ◽  
Axial Component ◽  
Profile Shape ◽  
Straight Flow

An experimental investigation of a low-speed turbulent swirling flow in a stationary, concentric, annular duct was made. The experiment involved isothermal air as the working fluid in an annulus with a diameter ratio di/d0 = 0.4, an average axial Reynolds number of 72,000, and an average axial velocity of 15 m/s. The swirl profile initially induced at the inlet was of the forced-vortex type. The rate of swirl, or the magnitude of the tangential velocity relative to the axial component, decayed axially from the inlet. Three different swirl rates were considered, one being straight flow. Extensive measurements were made of the velocity field with a cylindrical pressure probe at seven stations located 1.7 to 32.7 equivalent diameters from the entrance. The specific goals were experimental data on the axial decay of angular momentum and inferred values of the effective turbulent tangential viscosity. Results show a uniform axial decay of angular momentum and a profile shape independent of axial location. An empirical model using tangential eddy diffusivities that vary over the cross-section gave the best description of experimental data. The tangential profile shape and tangential viscosity distribution and magnitude did not depend on the initial rate of swirl.

scholarly journals Complex Flow Generation and Development in a Full-Scale Turbofan Inlet

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Tamara Guimarães ◽  
K. Todd Lowe ◽  
Walter F. O'Brien
Keyword(s):  
Secondary Flow ◽  
Full Scale ◽  
Stereoscopic Particle Image Velocimetry ◽  
Complex Flow ◽  
Mean Velocity ◽  
Ground Testing ◽  
Turbofan Engines ◽  
Flow Generation ◽  
Image Velocimetry ◽  
The Mean

The future of aviation relies on the integration of airframe and propulsion systems to improve aerodynamic performance and efficiency of aircraft, bringing design challenges, such as the ingestion of nonuniform flows by turbofan engines. In this work, we describe the behavior of a complex distorted inflow in a full-scale engine rig. The distortion, as in engines on a hybrid wing body (HWB) type of aircraft, is generated by a 21-in diameter StreamVane, an array of vanes that produce prescribed secondary flow distributions. Data are acquired using stereoscopic particle image velocimetry (PIV) at three measurement planes along the inlet of the research engine (Reynolds number of 2.4 × 106). A vortex dynamics-based model, named StreamFlow, is used to predict the mean secondary flow development based on the experimental data. The mean velocity profiles show that, as flow develops axially, the vortex present in the profile migrates clockwise, opposite to the rotation of the fan, and toward the spinner of the engine. The turbulent stresses indicate that the center of the vortex meanders around a preferred location, which tightens as flow gets closer to the fan, yielding a smaller radius mean vortex near the fan. Signature features of the distortion device are observed in the velocity gradients, showing the wakes generated by the distortion screen vanes in the flow. The results obtained shed light onto the aerodynamics of swirling flows representative of distorted turbofan inlets, while further advancing the understanding of the complex vane technology presented herein for advanced ground testing.

Confinement Effects on the Swirling Flow of a Counter-Rotating Swirl Cup

2005 ◽  
Author(s):  
Yongqiang Fu ◽  
Jun Cai ◽  
San-Mou Jeng ◽  
Hukam Mongia
Keyword(s):  
Test Section ◽  
Swirling Flow ◽  
Numerical Models ◽  
Effective Area ◽  
Aerodynamic Characteristics ◽  
Quality Data ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Radial Profiles

Gas turbine combustor’s performance, emissions, operability, liner and dome temperature levels and gradients are affected by the degree of confinement expressed indirectly by the dome reference velocity. An experimental investigation was therefore undertaken to characterize the aerodynamic characteristics of non-reacting swirling flow generated by a counter-rotating swirl cup as affected by the test section dimensions. A two-component Laser Doppler Velocimetry (LDV) system was used to measure the mean velocity components and Reynolds stresses of the flowfield generated by the swirl cup installed in 8 square box test sections with width of 3.0, 4.0, 4.1, 4.3, 4.4, 4.5, 5.0, and 6.0 inch, in addition to unconfined flow. Measurements were carried out at fourteen axial distances ranging from 3 to 250 mm downstream of the flare exit, and the radial profiles are obtained through 2 mm intervals. Detailed experimental data are provided to improve mechanistic understanding of the swirl cup generated flowfield as impacted by the ratio of the test section cross-section to the mixer’s effective area. The benchmark quality data are planned for validating the state-of-the-art numerical models in addition more advanced LES approach.

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