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  • INSTRUMENTATION AND PHOTOGRAPHY  (16)
  • ELECTRONICS AND ELECTRICAL ENGINEERING  (3)
  • SPACE SCIENCES  (1)
  • 1
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    The elusive third component (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 2
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    A comparison of turbulence intensity measurements using a laser velocimeter and a hot wire in a low speed jet flow (1982)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The study involves a simultaneous measurement with both instruments along radial scans at two axial locations in the jet exiting from the turbulent pipe and an axial scan at the 75-percent radial location in the jet from the convergent nozzle. The results suggest that, within the limits of flow stationarity, both instruments yield measurements in good agreement, + or - 0.8-percent in turbulence intensity, below a turbulence intensity (the ensemble standard deviation divided by the local mean velocity) of 20 percent. From turbulence intensities of 20 percent to a maximum of 75 percent, the measurements exhibit the same trends; for reasons discussed here, however, the comparisons are not of the quality as those below 20 percent. It is found that correcting the turbulence intensity data for velocity bias errors increases the results by an average of 2 percent in turbulence intensity above the hot wire results and the uncorrected laser velocimeter data. The results are seen as calling into question the validity of using the velocity bias correction and time average techniques for turbulence intensity measurements.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 3
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    Simultaneous Raman and laser velocimeter measurements (1974)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: AIAA Journal; 12; Oct. 197
    Format: text
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  • 4
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    Operational overview of Wallops Island instrument intercomparison - Carbon monoxide, nitric oxide, and hydroxyl instrumentation (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
    Format: text
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  • 5
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    Estimation of particle size based on LDV measurements in a de-accelerating flow field (1985)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Wind Tunnel Seeding Systems for Laser Velocimeters; p 29-51
    Format: application/pdf
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  • 6
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    Velocity vector analysis of a juncture flow using a three component laser velocimeter (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-12-01
    Beschreibung: A specialized single-axis, five-beam three-component laser velocimeter was constructed and used to study the flow field in a juncture. The juncture was defined by a blunt leading edged vertical splitter plate and a sharp leading edged horizontal plate. The investigations were conducted in the Low Turbulence Pressure Tunnel at a Mach number of 0.1 and a Reynolds number of 2.2 x 10 to the 6th per meter over the model. The three-component velocity flow field in the juncture was measured, Reynolds stresses calculated, and the velocity vector analysis performed.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 7
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    Comparison of hot wire/laser velocimeter turbulence intensity measurements (1982)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The question of whether a random measure of particle velocities yields a good statistical estimate of the stationary condition of the turbulence flow field was investigated by comparing hot-wire and laser velocimeter turbulence intensity measurements. Great care was taken to insure that the instrument precision of both the laser velocimeter and hot wire was maximized. In this attempt to reduce the measurement uncertainties in the hot wire, direct digitization of the analog output signal was performed with point-by-point conversion to velocity through a spline fit calibration curve and the turbulence intensity function was calculated statistically. Frequent calibrations of the hot wire were performed using the laser velocimeter as the velocity standard to account for the presence of the small seed particles in the air flow and signal drift in the hot wire.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Flow Visualization and Laser Velocimetry for Wind Tunnels; p 303-322
    Format: application/pdf
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  • 8
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    Frequency domain laser velocimeter signal processor (1986)
    In:  Other Sources
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    Publikationsdatum: 2018-12-01
    Beschreibung: 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.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
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  • 9
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    Frequency domain laser velocimeter signal processor (1986)
    In:  Other Sources
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    Publikationsdatum: 2018-12-01
    Beschreibung: A laser velocimeter frequency domain signal processor is described which utilizes smart instrumentation to configure itself to maximize measurement accuracy based on the determined characteristics of the input signals. The stystem provides the same measurement capabilities as the high-speed burst counter in instantaneous measurements of signal frequency, the same automatic gain control and automatic frequency control as the frequency tracker, and the same immunity to signal-to-noise derived errors as the photon correlator. Simulation results demonstrate measurement accuracies of better than 0.2 percent for signal frequencies up to 100 MHz.
    Schlagwort(e): ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 10
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    Skylab experiment performance evaluation manual (1972)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A series of preparation analyses used for evaluating the performance of the Skylab corollary experiments under preflight, in-flight, and postflight conditions is given. Experiment continegency plan work-around procedure and malfunction analyses are presented in order to assist in making the experiment operationally succesful.
    Schlagwort(e): SPACE SCIENCES
    Materialart: NASA-CR-61386
    Format: application/pdf
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