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  • 1
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    Temporal and spatial distribution of exhumed topography (1984)
    In:  CASI
    Details
    Publication Date: 2006-04-06
    Description: Perhaps the greatest chance for exhumation, or burial, of a landscape by terrestrial processes exists near the boundaries of the climatic belts. In the Southern Hemisphere, there is comparatively little land area within Budel's zone of extra-tropical valley formation, which contains most of the examples of exhumed topography in the Northern Hemisphere. The only examples of resurrected landforms that occur within Budel's tropical zone are located near the boundary of this zone, where climate may have changed during the Pleistocene. The ages of exhumed landforms sampled are not equally distributed through geologic time. Most of the exhumed features were created either during the Precambrian or the Tertiary periods which are commonly cited as episodes of significant landform development.
    Keywords: GEOPHYSICS
    Type: NASA. Washington Rept. of Planetary Geology Program, 1983; p 240-242
    Format: text
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  • 2
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    Moire deflectometry with deferred analysis (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A simplified version of moire deflectometry for flow visualization is presented. The modification comprises replacement of the second grating, the ground glass screen, and the camera with a plate film holder to obtain a shadow picture. Postanalysis proceeds by placing a grid transparency of the same periodicity of the remaining glass grating on the negative for projection viewing. The rotational angle between the grating and the plate alters the moire fringe periodicity. Use of the method in studying flows is predicted to reveal weak density gradient areas and shocks.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 22; Mar. 1
    Format: text
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  • 3
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    Flow visualization in the Langley 0.3-meter Transonic Cryogenic Tunnel and preliminary plans for the National Transonic Facility (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Design problems associated with the integration of flow visualization in cryogenic facilities are discussed. The possible effects from the cryogenic environment (i.e., window distortion due to thermal contraction both in the mounts and in the window material itself and turbulence in the flow due to injected LN2) are examined. The flow visualization techniques studied are schlieren, shadowgraph, moire deflectometry, and holographic interferometry. The test beds for this work are a Langley in-house cryogenic test chamber and the 0.3-Meter Transonic Cryogenic Tunnel.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Flow Visualization and Laser Velocimetry for Wind Tunnels; p 117-132
    Format: application/pdf
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  • 4
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    Two-mirrored galvanometer laser light sheet generator (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Light sheets generated with either laser or noncoherent sources have found widespread application to flow visualization. Previous light sheet generating systems were usually dedicated to a specific viewing geometry. The technique with the most flexibility is the galvanometer mirror based laser light sheet system. A two-mirrored system was designed and developed to provide flexibility and adaptability to a wide range of applications. The design includes the capability to control the size and location of the laser light sheet in real time, to generate horizontal or vertical sheets, to sweep the sheet repeatedly through a volume, to generate multiple sheets with controllable separation and to rotate single or multiple laser light sheets. The system is capable of producing up to 12 sheets of laser light at an angular divergence of + or - 20 degrees. Maximum scan rate of any one line is 500 Hertz. This system has proven to be uniquely versatile and a patent has been applied for.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 88-4680
    Format: text
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  • 5
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    A Scanning laser-velocimeter technique for measuring two-dimensional wake-vortex velocity distributions (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A rapid scanning two dimensional laser velocimeter (LV) has been used to measure simultaneously the vortex vertical and axial velocity distributions in the Langley Vortex Research Facility. This system utilized a two dimensional Bragg cell for removing flow direction ambiguity by translating the optical frequency for each velocity component, which was separated by band-pass filters. A rotational scan mechanism provided an incremental rapid scan to compensate for the large displacement of the vortex with time. The data were processed with a digital counter and an on-line minicomputer. Vaporized kerosene (0.5 micron to 5 micron particle sizes) was used for flow visualization and LV scattering centers. The overall measured mean-velocity uncertainity is less than 2 percent. These measurements were obtained from ensemble averaging of individual realizations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TP-1661 , L-13426
    Format: application/pdf
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  • 6
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    Optical scanning system for laser velocimeter (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An optical system was developed to provide fast incremental scanning of a backscattered laser velocimeter focus point over a 36-cm distance. The system is used to measure flow velocities at 16 positions along its optical axis and to scan these 16 positions up to 30 times a second. Dwell time at each location is approximately 2 milliseconds. Sample volumes typically are 0.2 mm in diameter by 1.4 cm in length. The optical scanning system consists of a wheel containing plane parallel quartz windows of various thicknesses. The laser velocimeter beams are imaged to a primary focus within the dead airspace of an optical cell. The beams emerging from the cell pass through the windows of the scanning wheel. The refraction of the beams passing through the windows causes an apparent shift of the focus within the optical cell and hence in the test zone. Light scattered from the secondary focus within the test zone is concurrently collected and reimaged through the same optical path which originally projected the primary focus. The reimaged backscattered light containing the velocity information is then collected and focused onto a photomultiplier detector system to complete the scanned laser velocimeter optical system.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Seminar on Laser scanning components and techniques: Design considerations/trends; Aug 24, 1976 - Aug 25, 1976; San Diego, CA
    Format: text
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