Download or read book Laser Doppler Velocimeter Measurements in High Speed Flows written by H. Doyle Thompson and published by . This book was released on 1974 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three year research program covering the development and use of a Laser Doppler Velocimeter (LDV) for high speed flow measurements is described. The current configurations of the LDV optics and the high frequency signal processors are discussed. LDV measurements made in two-dimensional transonic nozzles and in the turbulent wake of an axisymmetric supersonic nozzle are presented. These are compared with previous experimental and analytical results. Excellent agreement is found to exist. Measurement problems presented by flows of extremely high turbulence intensity are illustrated and means for resolving them are discussed.

Download or read book Laser Doppler Velocimeter Measurements of Boundary Layer Velocity and Turbulent Intensities in Mach 2 5 Flow written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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...

Download or read book Laser Velocimetry in Fluid Mechanics written by Alain Boutier and published by John Wiley & Sons. This book was released on 2013-01-09 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Turbulence Measurements with a Laser Doppler Velocimeter written by William Joseph Yanta and published by . This book was released on 1973 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Download or read book The Use of a Laser Doppler Velocimeter in Supersonic Flow written by William Joseph Yanta and published by . This book was released on 1971 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Download or read book Laser Doppler Velocimeter and High Speed Imaging System for Fluid Dynamics Combustion and Chemical Kinetics Research written by Yaw Yeboah and published by . This book was released on 1999 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Laser Doppler Velocimetry (LDV) system and a high speed imaging system were acquired for the Department of Defense (DoD) Grant N00014-97-1-0511 and setup in the Combustion and Emission Control Laboratory at Clark Atlanta University. These instruments have provided an integrated diagnostic system in the areas of combustion, propulsion, emission control, chemical kinetics and fluid dynamics for time resolved flow visualization and detailed quantitative measurements of flow velocities in complex reacting and non-reacting flows. Research projects supported with the acquired instruments included: turbulent premixed combustion, optimization of non-thermal plasma discharge for pollution control, droplet behavior under supercritical conditions, interaction between acoustic waves and fuel droplets and sprays, and combustion instabilities in ramjet combustors. The instruments will also be used on the precombustion pyrolytic degradation of hydrocarbon fuels under normal and microgravity conditions. Seven (7) undergraduate and graduate students from the Department of Engineering and Department of Chemistry at Clark Atlanta University have, so far, been trained and educated on the instruments. The acquired instrumentation has significantly strengthened the University's research infrastructure, and enhanced CAU's capabilities to undertake research that is relevant to the critical technology areas of DoD. These include the chemical kinetics, combustion and propulsion, and fluid dynamics programs of the Army Research Lab (ARL); the aerodynamics, turbulence and internal flows, air-breathing combustion, space power and propulsion, and physical mathematics and applied analysis programs of the Air Force Office of Scientific Research (AFOSR); and the turbulence, propulsion and flow structure interactions, and propulsion programs of the Office of Naval Research (ONR).

Download or read book Laser Velocimeter Measurements in Turbulent and Mixing Flows written by Warren H. Stevenson and published by . This book was released on 1979 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental and analytical study of subsonic flow over a rearward facing step is reported. A major emphasis of the work is the investigation of bias errors in mean velocities obtained from laser doppler velocimeter (LDV) measurements in such highly turbulent flows. Optical alignment of the specially designed LDV used in the study is described in detail. An analysis of the biasing problem is presented and preliminary measurements which appear to confirm previously predicted velocity bias errors are reported. Results of a computer model developed to describe the flow are presented together with preliminary static pressure measurements made in the flow facility. (Author).

Download or read book Doppler Global Velocimetry Measurements for Supersonic Flow Fields written by James F. Meyers and published by BiblioGov. This book was released on 2013-07 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The application of Doppler Global Velocimetry (DGV) to high-speed flows has its origins in the original development of the technology by Komine et al (1991). Komine used a small shop-air driven nozzle to generate a 200 m/s flow. This flow velocity was chosen since it produced a fairly large Doppler shift in the scattered light, resulting in a significant transmission loss as the light passed through the Iodine vapor. This proof-of-concept investigation showed that the technology was capable of measuring flow velocity within a measurement plane defined by a single-frequency laser light sheet. The effort also proved that velocity measurements could be made without resolving individual seed particles as required by other techniques such as Fringe- Type Laser Velocimetry and Particle Image Velocimetry. The promise of making planar velocity measurements with the possibility of using 0.1-micron condensation particles for seeding, Dibble et al (1989), resulted in the investigation of supersonic jet flow fields, Elliott et al (1993) and Smith and Northam (1995) - Mach 2.0 and 1.9 respectively. Meyers (1993) conducted a wind tunnel investigation above an inclined flat plate at Mach 2.5 and above a delta wing at Mach 2.8 and 4.6. Although these measurements were crude from an accuracy viewpoint, they did prove that the technology could be used to study supersonic flows using condensation as the scattering medium. Since then several research groups have studied the technology and developed solutions and methodologies to overcome most of the measurement accuracy limitations.

Download or read book Application of Laser Doppler Velocimeter to Chemical Vapor Laser System written by Luther R. Gartrell and published by . This book was released on 1993 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Use of the Laser Doppler Velocimeter for Flow Measurements written by Warren H. Stevenson and published by . This book was released on 1972 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Accuracy of Flow Measurements by Laser Doppler Methods written by Preben Buchhave and published by . This book was released on 1976 with total page 748 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Laser Doppler Velocimeter for Measurement of Flows Induced by Flames Propagating Over Condensed Fuels written by R. J. Santoro and published by . This book was released on 1974 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary process in the spread of fire along the surface of a condensed fuel is heat transfer from the burning region of the fuel to the material ahead of the flame. In the early stages of a fire, the two mechanisms by which this heat transfer occurs are conduction and convection ahead of the flame through the gas and fuel phases. The determination of the importance of the convective heat transfer can be ascertained only by accurate measurement of the fluid flow velocity and temperature fields near the flame front. Convective flows induced by spreading flames are characterized by low fluid velocities with changes in magnitude and direction accompanied by sharp temperature changes occurring over small distances. The bulk gas velocity induced by the flame frequently opposes the propagation. In liquids, there exists, as well, a liquid motion in the direction of the propagation of the flame. These characteristics make quantitative measurements of fluid velocities difficult using conventional techniques. With the advent of Laser Doppler Velocimeter (LDV) techniques, a non-perturbing means of making high resolution measurements of two-dimensional low velocity fields now exists. Thus, the possibility of determining the role of convective effects has become realizable.

Download or read book Development of a Laser Doppler Velocimetry System for Supersonic Jet Turbulence Measurements written by Alex Karns and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of military style exhaust nozzles to further understand their acoustic characteristics has been the recent focus of the Pennsylvania State University high-speed jet aeroacoustics facility. Advanced measurement techniques are required to study the turbulence characteristics of the flow field. Development of a laser Doppler velocimetry system would allow for these measurements to be made non-intrusively.Development of the laser Doppler velocimetry system required research and testing of each component as it was placed into the system. Development was split into two portions: fundamental or basic concepts and components, and advanced components. During these stages, many components, such as the transmitting and receiving probes, were fabricated, procedures were developed, and calibration of the transmitting probe was completed.Once the development stages were complete, the laser Doppler velocimetry system was used to measure subsonic flows of a cold air exhaust jet. Velocity measurements proved to be accurate to within 2% of calculated jet Mach numbers with discrepancies of up to 6% at Mach numbers approaching 1 at x/D of 2. Comparison of axial turbulence intensity data to previous studies yielded less favorable result possibly due to use of the exhaust fan, but this hypothesis cannot be proven without more experiments.Parametric studies were also on the ratio of the injection pressure ratio to the nozzle pressure ratio and the exhaust fan power determine their effects of seeding on measurement values. It was determined that ratio of the injection pressure ratio to the nozzle pressure ratio had negligible effect on the measurements except at a value of 1 where the axial turbulence intensity was up to 6% different than the other measurements. However, the ratio was found to have an inverse relationship to the number of validated burst particles per unit time. The power of the exhaust fan created differences in the measurement of up to 3% at x/D greater than 6, with higher values of Mach number and lower values of axial turbulence intensity at the exhaust fan power of 15%. However, it is difficult to draw conclusions with only two sets of data.

Download or read book Optical Measurements written by Franz Mayinger and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing possibilities of computer-aided data processing have caused a new revival of optical techniques in many areas of mechanical and chemical en gineering. Optical methods have a long tradition in heat and mass transfer and in fluid dynamics. Global experimental information is not sufficient for developing constitution equations to describe complicated phenomena in fluid dynamics or in transfer processes by a computer program . Furthermore, a detailed insight with high local and temporal resolution into the thermo-and fluiddynamic situations is necessary. Sets of equations for computer program in thermo dynamics and fluid dynamics usually consist of two types of formulations: a first one derived from the conservation laws for mass, energy and momentum, and a second one mathematically modelling transport processes like laminar or turbulent diffusion. For reliably predicting the heat transfer, for example, the velocity and temperature field in the boundary layer must be known, or a physically realistic and widely valid correlation describing the turbulence must be avail able. For a better understanding of combustion processes it is necessary to know the local concentration and temperature just ahead of the flame and in the ignition zone.

Download or read book Application of a Novel Laser Doppler Velocimeter for Turbulence Structural Measurements in Turbulent Boundary Layers written by and published by . This book was released on 2006 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: An advanced laser-Doppler velocimeter (LDV), deemed the 'comprehensive LDV', is designed to acquire fully-resolved turbulence structural measurements in high Reynolds number two- and three-dimensional turbulent boundary layers. The new instrument combines, for the first time, new techniques allowing for the direct measurement of particle acceleration and sub-measurement-volume-scale position resolution so that second-order 3D particle trajectories may be measured at high repetitions. Using these measurements, several terms in the Reynolds stress transport equations may be directly estimated, giving new data for modeling and understanding the processes leading to the transport of turbulence in boundary layer flows. Measurements utilizing the CompLDV technologies are presented and include turbulence dissipation rate and fluctuating velocity-pressure gradient correlations that have been measured in 2D and 3D turbulent boundary layers using the unique capabilities of the 'comprehensive' LDV. Many of these measurements are the first of their kind ever acquired in high Reynolds number turbulent flows. The flat-plate turbulent boundary layer is studied at several Reynolds numbers up to Re-theta ~7500 to examine Reynolds numbers effects on terms such as the velocity-pressure gradient correlation and the dissipation rate in the Reynolds transport equations. Measurements are also presented in a pressure-driven three-dimensional turbulent boundary layer created upstream from a wing-body junction. The current results complement the extensive data from previous studies and provide even richer depth of knowledge on the most completely-documented 3D boundary layer flow in existence. Further measurements include the effects of high free-stream turbulence on flat plate turbulent boundary layers and a wing/body junction flow that is similar to a gas turbine flow.

Download or read book The Use of a Laser Doppler Velocimeter in Supersonic Flow written by William J. Yanta and published by . This book was released on 1971 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Download or read book Steady Flow Field Measurements Using Laser Doppler Velocimetry written by Ricky E. Wilson and published by . This book was released on 1987 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computer-integrated LDV system utilizing a Helium-Neon laser was designed, assembled and tested for use in the study of steady flow field quantities. All system elements were integrated to include a traverse mechanism, signal processing and conditioning, computer interface and display. The system was initially calibrated utilizing a rotating wheel of known velocity. Experimental flow measurement tests of the system were conducted across a conventional free jet flow and in the Naval Postgraduate School low speed wind tunnel. The flow field velocity measurements made in the wind tunnel were verified usin an existing pressure data acquisition station and a standard pitot static probe. Keywords: Laser doppler velocimetry.