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Author: William Joseph Yanta
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 64
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Book Description
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).
Author: William Joseph Yanta
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 64
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Book Description
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).
Author: William J. Yanta
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
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).
Author: J. C. Donaldson
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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Book Description
Laser Doppler velocimeter techniques have been investigated for nonintrusive measurements of cone boundary-layer mean-velocity profiles in supersonic flow. The investigation was performed in the AEDC Supersonic Wind Tunnel (A) at a free-stream Mach number of 4, using olive-oil droplets to seed the tunnel flow. The basis for the evaluation of the LDV results was a set of velocity profiles obtained using conventional probing techniques. Laminar, transitional, and turbulent boundary layers on a 7-deg (half-angle) sharp-cone model were included in this study. The results obtained in this investigation demonstrate that mean-velocity profiles can be obtained within acceptable limits of uncertainty provided (1) seed particles of appropriate size are found in tunnel flow or can be added to the flow and (2) a systematic editing procedure is available, when the results are evaluated, to eliminate velocities of relatively low probability and effects of spurious noise. (Author).
Author: Luther R. Gartrell
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
Author: Paul E. Dimotakis
Publisher:
ISBN:
Category :
Languages : en
Pages : 89
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Book Description
Experiments have been carried out using laser-Doppler velocimetry in conjunction with Pitot and surface-friction instrumentation for the measurement of the mean flow, the velocity fluctuations, and the Reynolds stresses in turbulent boundary layers at constant pressure in subsonic and supersonic flows. Part I of this work was a detailed analysis of the mean flow as observed using Pitot-tube, Preston-tube, and floating-element balance instrumentation. The present work (Part II) is a description of both the mean and the fluctuating components of the flow, and of the Reynolds stress as observed using a dual forward-scattering laser-Doppler velocimenter. A detailed description of the instrument, and of the data analysis techniques, have been included in order to fully document the data. A detailed comparison is made between the laser-Doppler results and those presented in Part I, and an assessment is made of the ability of the laser-Doppler velocimeter to measure the details of the flows involved.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722335045
Category :
Languages : en
Pages : 34
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Book Description
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...
Author: H. Tracy Jackson (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages : 110
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Book Description
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).
Author: Alex Karns
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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.
Author: Stanford University. Department of Aeronautics and Astronautics
Publisher:
ISBN:
Category :
Languages : en
Pages : 362
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Book Description
In chemical propulsion, the use of metallic fuel constituents burning to particulate refractory oxides in rocket engines has forced attention to the understanding of two-phase nozzle expansion processes. In this study light from a helium-neon laser was reflected both from a fixed target and from moving particles. A lens concentrated the laser light and the light back-scattered from the particles was picked up by the same lens and directed into a Fabry-Perot scanning plate interferometer. The interferometer limited observation at any moment to those particles whose Doppler shifted frequency coincided with the interferometer transmission frequency. The light from the fixed target provided a frequency reference system, and calibrated movement of the interferometer mirror spacing provided continuous examination of velocity. Data in the form of lightscattering and number count vs velocity has been obtained for water droplets in subsonic flow, for aluminum spheres and alumina abrasive in cold supersonic flow and for aluminum and magnesium oxide in hot supersonic flow. Number count-velocity data was found to be a complicated function of particle size distribution and vector velocity distribution as well as instrument characteristics.
Author: William Joseph Yanta
Publisher:
ISBN:
Category : Laser Doppler velocimeter
Languages : en
Pages : 104
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Book Description
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).
