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  • 1
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    Supercooling in hypersonic nitrogen wind tunnels (1994)
    Cambridge University Press
    Details
    Publication Date: 1994-06-25
    Description: Recent experimental observation of supercooling in large hypersonic wind tunnels using pure nitrogen identified a broad range of non-equilibrium metastable vapour states of the flow in the test cell. To investigate this phenomenon a number of real-gas effects are analysed and compared with predictions made using the ideal-gas equation of state and equilibrium thermodynamics. The observed limit on the extent of supercooling is found to be at 60 % of the temperature difference from the sublimation line to Gibbs’ absolute limit on phase stability. The mass fraction then condensing is calculated to be 12-14%. Included in the study are virial effects, quantization of rotational and vibrational energy, and the possible role of vibrational relaxation and freezing in supercooling. Results suggest that use of the supercooled region to enlarge the Mach-Reynolds number test envelope may be practical. Data from model tests in supercooled flows support this possibility. © 1994, Cambridge University Press
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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    PAPER CURRENT
  • 2
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    Quantification of vapor screen analysis (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The traditionally qualitative method of vapor screening is applied to the task of gathering quantitative density measurements in supersonic flows. Quantitative density information for flow around a two-dimensional biconvex airfoil at Mach 2.8 is extracted from digitized images of vapor screens by assuming a linear relation between particle density and scattering intensity. Intensity readings are calibrated through known conditions in the free stream and at the airfoil bow shock. The experimental results are compared to densities generated by a Euler code and determined to have errors of less than ten percent.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-1691
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Laser holographic interferometric measurements of the flow in a scramjet inlet at Mach 4 (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The need for quantitative data is addressed by laser holographic interferometry (LHI) by efficiently recording and reducing high resolution density data. This paper investigates the potential to get quantitative data from an interferogram created from two separate holographic plates. THe LHI measurements were made on a scramjet inlet at Mach 4. LHI successfully generated results for both internal and external flows, and demonstrated its ability to map entire flow fields. Of the three data reduction techniques used, the four-bucket method gave better results than the three-bucket or three-by-three methods. This technique requires high quality holograms as well as a good resolution in the digital images to produce good data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-0043
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Condensation in hypersonic nitrogen wind tunnels (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Experimental observations and a theoretical model for the onset and disappearance of condensation are given for hypersonic flows of pure nitrogen at M = 10, 14 and 18. Measurements include Pitot pressures, static pressures and laser light scattering experiments. These measurements coupled with a theoretical model indicate a substantial non-equilibrium supercooling of the vapor phase beyond the saturation line. Typical results are presented with implications for the design of hypersonic wind tunnel nozzles.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 90-1392
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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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
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    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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  • 6
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    Condensation shocks in hypersonic nitrogen tunnels (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Experimental observations and a theoretical model for the onset and disappearance of condensation are provided for hypersonic flows of pure nitrogen at M = 10, 14, and 18. A method for analyzing the thermodynamic and flow properties of a partially condensed mixture from known supply conditions and measured Pitot pressure yields the local static pressure and temperature, mass fraction of the nitrogen condensed, and the Mach number of the partially condensed flow based on frozen sound speed. The transition between partially condensed-supercooled flow is found to occur at 22-25 K isobaric supercooling with the corresponding mass fraction condensed being 12-14 percent over a range of two orders of magnitude in local static pressure. The heat released and vapor mass removed during condensation ultimately raise the local pressure and temperature and reduce the flow Mach number.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: International Symposium on Shock Waves and Shock Tubes; Jul 17, 1989 - Jul 21, 1989; Bethlehem, PA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Boundary layer study on nozzle wall at hypersonic velocities (1992)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The boundary layer on the wall of the Hypervelocity Tunnel 9 was investigated with pitot pressure and total temperature measurements. Experimental results are presented for standard and supercooled Mach 14 runs. The boundary layer data at supercooled conditions are compared to numerical predictions made with a Navier-Stokes algorithm including vibrational nonequilibrium and intermolecular force effects. For standard tunnel conditions, the numerical solutions agree well with experimental data. For the supercooled cases, the numerical code predicts the total temperature but overpredicts the pitot pressure.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-4013
    Format: text
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