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:

DOWNLOAD EBOOK

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).

Three-Dimensional Velocity and Vorticity Measuring and Image Analysis Techniques
Three-Dimensional Velocity and Vorticity Measuring and Image Analysis Techniques

Author: Th. Dracos

Publisher: Springer Science & Business Media

Published: 1996-10-31

Total Pages: 346

ISBN-13: 9780792342564

DOWNLOAD EBOOK

The contents of this volume reflect to a large extent the efforts made by a group of Institutes at the ETH Zürich to develop new techniques for measurements of flows in fluids in the last decade. The motivation came from the study of tr~sport and mixing processes in natural and industrial systems. One of the characteristic properties of turbulence is its high mixing efficiency. The techniques developed are therefore suitable, although not exclusively, for turbulence measurements. They can be subdivided into point-measurements and field-measurements. The aim of the point-measurements developed is to determine the three components of the velocity and all their first derivatives with good temporal resolution and accuracy in turbulent flows. The old and weIl established method of hot-wire anemometry was used for this purpose. One of the main achievements in this context is the construction of miniature multi-wire probes. This technique was introduced to the Institute of Hydromechanics and Water Resources Management of ETH Zürich by Profs. A. Tsinober and E. Kit from Tel-Aviv University. This was made possible by the generous financial support by ETH, for which I would like to express my gratitude on this occasion. In addition, Dr. F.E. Joergensen from DANTEC contributed an example of recent developments in the hardware ofConstant Temperature Anemometry (CTA), for which I am very thankful.

Three Dimensional Laser Doppler Velocimeter Measurements of the Velocity Distribution in a Supersonic Jet Mixing with a Subsonic Outer Flow
Three Dimensional Laser Doppler Velocimeter Measurements of the Velocity Distribution in a Supersonic Jet Mixing with a Subsonic Outer Flow

Author: H. Tracy Jackson (Jr)

Publisher:

Published: 1975

Total Pages: 110

ISBN-13:

DOWNLOAD EBOOK

Three-dimensional laser doppler velocimeter measurements were made of the velocity distribution in a supersonic inner jet mixing with a subsonic outer flow. Experimental data for mean flow velocities (u, v, w), turbulent intensities ((u') squared, (v') squared, (w') squared), and turbulent velocity correlations (u'v', u'w', v'w) are presented for both hot and cold exhaust plumes produced by a small kerosene/gaseous oxygen rocket engine operating at nominal chamber pressures of 50 and 150 psig. The outer flow was maintained at 200 ft/sec. Velocity profiles were obtained in the radial direction at various axial locations (X/D sub E=2.4, 4.8, 8.4, 11.3, and 14.2). The velocity profile along the centerline of the jet was obtained for the cold flows and showed the presence of shock waves at various axial locations. (Author).

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

DOWNLOAD EBOOK

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...

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:

DOWNLOAD EBOOK

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).