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  • 1
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    A method of analyzing holographic interferograms of ballistic models in hypersonic free-flight (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The objective of this research was to develop a method to extract integrated flowfield density information from finite-fringe interferograms produced with a laser holographic interferometer. This method was applied to two sets of holograms. An aeroassist flight experiment model flown in a mixture of 50 percent air - 50 percent argon and a blunt slender cone flown in air were flown at Mach 14.5 into freestream static pressures of 0.04 and 0.08 atm, respectively. The method of analysis can be separated into two main divisions. The first step is to identify fringes inside the wake in terms of the fringes in the freestream. This is important because refraction effects have obscured the region near the shock such that fringes cannot be followed into the wake region. The second step is to extrapolate the freestream fringes into the wake to determine the location of disturbance-related fringe shifts. Coupled with assumptions about the shape of the wake region, the locations of the disturbance-related fringe shifts can be related to the integrated density.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 92-0378
    Format: text
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  • 2
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    Infrared imaging and tufts studies of boundary layer flow regimes on a NACA 0012 airfoil (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A study of boundary-layer flow regimes on a NACA 0012 airfoil from zero angle of attack up to separation is presented. The boundary-layer transition from the laminar to the turbulent regime and the onset of the separation were detected by surface thermography of the airfoil performed with an infrared imaging system. The findings were compared with observations of aluminum-foil tufts visible with the infrared imaging system. This arrangement allows the infrared imaging system to assume the dual role of flow regime detection through surface thermography and flow visualization through the observation of the aluminum-foil tufts. Ultimately the temperature history on an uncontaminated surface could provide an interpretation of the state of boundary-layer flow. Separation studies performed on the NACA 0012 airfoil showed that aluminum foil tufts can be observed with infrared imaging systems.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''89; Sept. 18-21, 1989; Goettingen; Germany
    Format: text
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  • 3
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    New devices for flow measurements: Hot film and burial wire sensors, infrared imagery, liquid crystal, and piezo-electric model (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: An experimental program aimed at identifying areas in low speed aerodynamic research where infrared imaging systems can make significant contributions is discussed. Implementing a new technique, a long electrically heated wire was placed across a laminar flow. By measuring the temperature distribution along the wire with the IR imaging camera, the flow behavior was identified.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-187911 , NAS 1.26:187911
    Format: application/pdf
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  • 4
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    A fine-wire thermocouple probe for measurement of stagnation temperatures in real gas hypersonic flows of nitrogen (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: A fine-wire thermocouple probe was used to determine freestream stagnation temperatures in hypersonic flows. Data were gathered in a N2 blowdown wind tunnel with runtimes of 1-5 s. Tests were made at supply pressures between 30 and 1400 atm and supply temperatures between 700 and 1900 K, with Mach numbers of 14 to 16. An iterative procedure requiring thermocouple data, pilot pressure measurements, and supply conditions was used to determine test cell stagnation temperatures. Probe conduction and radiation losses, as well as real gas behavior of N2, were accounted for during analysis. Temperature measurement error was found to be 5 to 10 percent. A correlation was drawn between thermocouple diameter Reynolds number and temperature recovery ratio. Transient probe behavior was studied and was found to be adequate in temperature gradients up to 1000 K/s.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''91 - International Congress on Instrumentation in Aerospace Simulation Facilities; Oct 27, 1991 - Oct 31, 1991; Rockville, MD; United States
    Format: text
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  • 5
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    Aerodynamic investigation by infrared imaging (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Infrared imaging systems can be used to measure temperatures of actively heated bodies immersed in an airstream. This monitoring of the convective heat transfer process, provides also information about the interaction between the body and the flow. The concept appeals to Nusselt/Reynolds numbers relations in order to produce data of interest from surface temperatures. Two test cases are presented and reference is made to analytical results: the mapping of a laminar jet and the temperature distribution along a constant power heated flat plate in laminar boundary layer regime. Although this research is currently focused on low speed aerodynamics, the extension to high speed aerodynamics, where the body undergoes frictional heating is of interest in this context, too.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 88-2523 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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  • 6
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    Model of hot-film sensor with substrate (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A detailed model is constructed to investigate parameters influencing a hot-film anemometer system used to study cross-flow phenomena on swept wings. This anemometer is designed to detect vortices set up by cross-flow. The nature of the vortices is not well known, and a well-verified instrumentation model is considered essential to allow accurate interpretation of experimental results. Previous investigators have indicated that heat conduction to the film's substrate is significant. Two variations on the inclusion of substrate effects in the model are discussed. In the first, the substrate is assumed to have a constant temperature throughput: in the second more elaborate model, the temperature of the substrate is allowed to vary. This variation is related to the convective heat removal at the substrate/gas interface.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''87 - International Congress on Instrumentation in Aerospace Simulation Facilities; Jun 22, 1987 - Jun 25, 1987; Williamsburg, VA; United States
    Format: text
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