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  • INSTRUMENTATION AND PHOTOGRAPHY  (4)
  • MECHANICS
  • 1985-1989  (4)
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  • 1
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    Unknown
    The elusive third component (1985)
    In:  Other Sources
    Details
    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
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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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
  • 3
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    Unknown
    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
  • 4
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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
    Format: text
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