Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion. Part 3. A Correction Lens for Laser Doppler Measurements in a Cylindrical Tube
Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion. Part 3. A Correction Lens for Laser Doppler Measurements in a Cylindrical Tube

Author: H. D. Thompson

Publisher:

Published: 1984

Total Pages: 207

ISBN-13:

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A lens was designed using analytical ray tracing techniques to correct aberrations caused by a cylindrical tube wall when measurements are made off the plane of symmetry with a Laser Doppler Velocimeter. The single element correction lens was found to work well and good results were obtained out to a normalized tube radius of r/R = 0.83. LDV measurements were made in three axisymmetric flow geometries: a turbulent flow in a straight pipe, a sudden expansion with diameter ratio 1.90:1, and a second sudden explosion with diameter ratio 2.70:1. Mean velocity and turbulence intensity were measured as well as Reynolds stress and turbulence kinetic energy. Numerical predictions of the flow field using the k-epsilon turbulence model were compared to the experimental measurements in the 1:90:1 sudden expansion. In the 2.70:1 sudden expansion, the presence of a secondary recirculation zone in the corner of the step was confirmed and velocity measurements were made in this region. (Author).

Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion. Part 4. Two-Component Cold-Flow Measurements
Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion. Part 4. Two-Component Cold-Flow Measurements

Author: H. D. Thompson

Publisher:

Published: 1986

Total Pages: 36

ISBN-13:

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A unique two component, two color Laser doppler Velocimeter (LDV) has been designed and built. The system includes Bragg cell modulators in all four beams, and a correction lens system to correct for the aberration induced by the cylindrical quartz test section. A dedicated PDP 11/40 mini-computer with DMA capability is used for data collection, storage, and processing. Two component (axial and radial) velocity measurements have been made in the turbulent flow field following an axisymmetric sudden expansion. Mean streamwise and radial velocity and turbulence intensity measurements were made. Reynolds stresses were computed. Keywords: Turbulent measurements; Laser velocimeter; Bias errors; Recirculating flows.

Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion
Laser Velocimeter Measurements and Analysis in Turbulent Flows with Combustion

Author: Warren H. Stevenson

Publisher:

Published: 1982

Total Pages: 93

ISBN-13:

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Laser velocimeter measurements of mean velocities and turbulence parameters were made in a cylindrical simulated dump combustor. Velocity bias errors were eliminated by use of an experimental technique developed in an earlier study. a comparison of mass flux at different downstream locations based on the measured velocity profiles showed good agreement with the inlet mass flux. The measured mean velocity profiles were in good qualitative agreement with predictions based on the 2/E/FIX computer code, although some discrepancies in qualitative values due to code limitations were noted. (Author).

Laser Velocimetry in Fluid Mechanics
Laser Velocimetry in Fluid Mechanics

Author: Alain Boutier

Publisher: John Wiley & Sons

Published: 2013-01-09

Total Pages: 436

ISBN-13: 1118569334

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In fluid mechanics, velocity measurement is fundamental in order to improve the behavior knowledge of the flow. Velocity maps help us to understand the mean flow structure and its fluctuations, in order to further validate codes. Laser velocimetry is an optical technique for velocity measurements; it is based on light scattering by tiny particles assumed to follow the flow, which allows the local fluid flow velocity and its fluctuations to be determined. It is a widely used non-intrusive technique to measure velocities in fluid flows, either locally or in a map. This book presents the various techniques of laser velocimetry, as well as their specific qualities: local measurements or in plane maps, mean or instantaneous values, 3D measurements. Flow seeding with particles is described with currently used products, as well as the appropriate aerosol generators. Post-processing of data allows us to extract synthetic information from measurements and to perform comparisons with results issued from CFD codes. The principles and characteristics of the different available techniques, all based on the scattering of light by tiny particles embedded in the flow, are described in detail; showing how they deliver different information, either locally or in a map, mean values and turbulence characteristics.

Turbulence Measurements with a Laser Doppler Velocimeter
Turbulence Measurements with a Laser Doppler Velocimeter

Author: William Joseph Yanta

Publisher:

Published: 1973

Total Pages: 104

ISBN-13:

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Turbulence measurements with a Laser Doppler Velocimeter (LDV) using the dual scatter or differential Doppler mode have been made in a subsonic, fully developed channel flow. The measurements were made using only those light scattering particles occurring naturally in air. Results include mean velocity profiles, turbulence intensities, Reynolds stress distributions and a skewness measurement of the velocity distribution function across the channel. Statistical techniques were used to obtain the various turbulence parameters. Guidelines have been established for the amount of data needed to obtain results with a specified accuracy and confidence level. Measurements have also been made to determine the particle-size distribution. An aerodynamic means was used to determine the size distribution, in contrast to the usual optical procedures. (Modified author abstract).

Laser Velocimetry and Particle Sizing
Laser Velocimetry and Particle Sizing

Author: Howard Doyle Thompson

Publisher:

Published: 1979

Total Pages: 586

ISBN-13:

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Contents: A Historical Review of Laser Velocimetry. Developments in Instrumentation, Data Analysis, Combustion Measurements, Measurements in Turbulent Flows, Measurements in Internal Combustion Engines, General Applications, Particle Diagnostics, Wild Card Session, and Panel Discussion.

A Scanning Laser Velocimeter for Turbulence Research
A Scanning Laser Velocimeter for Turbulence Research

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-08-20

Total Pages: 32

ISBN-13: 9781725628250

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Turbulent and unsteady separated flows occur on most practical flight vehicles, but are not yet sufficiently understood for designs to provide safe margins of performance without recourse to extensive experiment and computation. In date, reliable experimental data for even basic flows is severely limited and does not yet provide a satisfactory data base with which to assess current design and calculation methods. Although the laser velocimeter (LV) has become a proven, nonintrusive instrument for the measurement of local mean velocities and turbulence properties, measurements have been of a mean, statistical nature derived from averages accumulated independently at different positions in the flow. Thus, the measurements do not give an instantaneous dynamic, picture of the flow-field structures. Accordingly, a new technique for rapid LV scans of turbulent flow fields was proposed. The potential of this new instrument for fundamental fluid mechanical measurements of turbulent flows has been demonstrated. The results clearly show that significant unsteady flow features are hidden by conventional measurements and that the scanning laser velocimeter should prove an invauable tool in future studies of the structure of turbulent flows. Duen, F. K. Unspecified Center NASA-CR-172493, NAS 1.26:172493 NAS1-17572; RTOP 324-01-00-01...

Laser Doppler Velocimeter Measurements of Boundary Layer Velocity and Turbulent Intensities in Mach 2. 5 Flow
Laser Doppler Velocimeter Measurements of Boundary Layer Velocity and Turbulent Intensities in Mach 2. 5 Flow

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-05

Total Pages: 34

ISBN-13: 9781722335045

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In recent years, the interest in developing a high-speed civil transport has increased. This has led to an increase in research activity on compressible supersonic flows, in particular the boundary layer. The structure of subsonic boundary layers has been extensively documented using conditional sampling techniques which exploit the knowledge of both u and v velocities. Researchers using these techniques have been able to explore some of the complex three-dimensional motions which are responsible for Reynolds stress production and transport in the boundary layer. As interest in turbulent structure has grown to include supersonic flows, a need for simultaneous multicomponent velocity measurements in these flows has developed. The success of conditional analysis in determining the characteristics of coherent motions and structures in the boundary layer relies on accurate, simultaneous measurement of two instantaneous velocity components. Sewell, Jesse and Chew, Larry Unspecified Center NAG1-1402...