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 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.

The Use of a Laser Doppler Velocimeter in Supersonic Flow
The Use of a Laser Doppler Velocimeter in Supersonic Flow

Author: William Joseph Yanta

Publisher:

Published: 1971

Total Pages: 64

ISBN-13:

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Results are presented for an experimental program which investigated the application of an LDV technique in supersonic flows. This paper presents an analysis of the behavior of light-scattering particles in rapidly accelerating or shock decelerated flows, an evaluation of particle production techniques and the results of several velocity measurements. Measurements included the velocity distribution along the nozzle centerline and flow over a diamond airfoil in a Mach 3 tunnel and velocity profiles for a turbulent boundary layer in a Mach 4.8 facility. It is demonstrated that LDV measurements can be made consistently with errors of less than five percent if the particle lag is considered. (Author).

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).