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  • INSTRUMENTATION AND PHOTOGRAPHY  (8)
  • 2000-2004
  • 1985-1989  (4)
  • 1970-1974  (4)
  • 1955-1959
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  • 1
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    The elusive third component (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The historical development of techniques for measuring three velocity components using laser velocimetry is presented. The techniques are described and their relative merits presented. Many of the approaches currently in use based on the fringe laser velocimeter have yielded inaccurate measurements of turbulence intensity in the on-axis component. A possible explanation for these inaccuracies is presented along with simulation results.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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    NASA TECHNICAL REPORTS
  • 2
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    Simultaneous Raman and laser velocimeter measurements (1974)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The feasibility of performing Raman and laser velocimeter measurements simultaneously is demonstrated, and it is shown that the background radiation associated with the Mie scattering and large particulate concentrations does not saturate or distort the relatively weak rotational Raman signals. Under stringent conditions of low static gas densities and large particulate concentrations, Raman density and temperature measurements agree to within plus or minus 5% of the calculated values.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal; 12; Oct. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Operational overview of Wallops Island instrument intercomparison - Carbon monoxide, nitric oxide, and hydroxyl instrumentation (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: NASA has initiated the Global Tropospheric Experiment (GTE) for the study of the chemistry of the global troposphere. One phase of GTE, Chemical Instrumentation Test and Evaluation (CITE), is concerned with the development and validation of measurement techniques for trace species which play important roles in the tropospheric chemical cycles. In connection with CITE 1 an intercomparison of instruments is conducted for the measurement of CO, NO, and OH. These species have been identified as critical for an understanding of homogeneous gas-phase chemistry in the troposphere. The present paper provides an operational overview of the first of three instrument intercomparison field missions conducted as part of GTE/CITE 1. The missions include one ground-based and two airborne missions, and were designed to characterize current capability of measuring ambient levels of CO, NO, and OH.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
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    NASA TECHNICAL REPORTS
  • 4
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    Estimation of particle size based on LDV measurements in a de-accelerating flow field (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The accuracy of velocity measurements made with a laser velocimeter is strongly dependent upon the response of the seeding particles to the dynamics of the flow field. The smaller the particle the better the response to flow fluctuations and gradients and therefore the more accurate velocity measurement. In direct conflict is the requirement of light scattering efficiency to obtain signals with the laser velocimeter which, in general, is better as the particle size is increased. In low speed flow fields these two requirements on particle size overlap and accurate measurements may be obtained. However in high speed flows, where the velocity gradients may be severe, very small particles are required to maintain sufficient dynamic response characteristics to follow the flow. Therefore if velocity measurements are to be made in these flows, the laser velocimeter must be designed with sufficient sensitivity to obtain signals from these small particles. An insitu determination of the size distribution of kaolin particles (Al2O3, .2 + or - SiO2 . 2H2O) in the 16-foot Transonic Tunnel and the sensitivity characteristics of the laser velocimeter system is described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Wind Tunnel Seeding Systems for Laser Velocimeters; p 29-51
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Frequency domain laser velocimeter signal processor (1986)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: The features and performance parameters of the frequency domain laser velocimeter signal processor (FDSP) for examining flow phenomena are described. A candidate for replacing the standard signal processor, the FDSP can function receiving bursts of as few as 150 photons in an instantaneous mode or down to a photon resolved regime for an averaging mode. the FDSP has a nonlinear A/D converter and data storage shift registers (high speed recorder group), an elliptic digital filter bank, a controlling microprocessor and frequency and signal gain control circuits (low speed data processing group). The high speed group amplifies, digitizes, identifies and stores burst waveforms and the low speed group identifies the signal frequency within the burst after the signal passes through digital filters. The FDSP can operate in a near-autonomous mode using photon correlation techniques and requires no human intervention for calibration.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
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    Processing of the laser Doppler velocimeter signals (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The laser Doppler velocimeter (LDV) is a probeless technique that provides a remote measurement of mean and fluctuating velocities. The measurement is actually obtained from small particles embedded in the flow which scatter light from an illuminating laser beam interference pattern. A portion of this scattered light is collected by a photomultiplier which yields an electronic signal whose frequency is directly proportional to the velocity of the small particles. The purpose of this paper is to describe and critically compare three techniques most used to process this electronic signal. These techniques are: (1) spectrum analyzer - a frequency scanning filter (frequency domain instrument), (2) wide-band frequency tracker - a frequency lock loop (frequency domain instrument), and (3) high-speed frequency counter - an interval timer (time domain instrument). The study determines the ability of each technique to process the LDV signal and yield velocity data to be used in determining the flow characteristics.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''73; International Congress on Instrumentation in Aerospace Simulation Facilities; Sep 10, 1973 - Sep 12, 1973; Pasadena, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Computer simulation of a fringe type laser velocimeter (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A computer simulation of a fringe type laser velocimeter has been written to determine the theoretical characteristics of the laser velocimeter when applied to a given flow field. The program includes the effect of particle size and composition on particle lag, light scattering characteristics and signal contrast. The model of the laser velocimeter includes the laser, optical system, photomultiplier, and counter type data processing electronics. The LV particle size analyzer is also modeled and incorporated in the program. An example application of the program to a Mach 5 wind tunnel using a backscatter laser velocimeter is presented.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: International Workshop on Laser Velocimetry; Mar 27, 1974 - Mar 29, 1974; West Lafayette, IN
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    NASA TECHNICAL REPORTS
  • 8
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    A feasibility test of the laser velocimeter in the Mach 5 nozzle test chamber (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A one-component, fringe type laser velocimeter in the backscatter mode was used to measure flow velocities from 732 to 792 m/sec about a shock from an inclined flat plate in a Mach 5 tunnel. This test was chosen to determine system characteristics in applying the laser velocimeter to measure velocities in hypersonic flow fields. The seeding particles, less than 20 microns in diameter, were injected into the tunnel supply pipe, approximately 1 meter upstream of the nozzle throat, through a rake along the diameter. The LV signals were processed by two methods, a scanning spectrum analyzer and a high-speed counter. The measured velocity distributions obtained were analyzed to determine the errors due to particle lag, transit time broadening and high-speed counter quantizing error.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: International Workshop on Laser Velocimetry; Mar 27, 1974 - Mar 29, 1974; West Lafayette, IN
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