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  • 1995-1999  (7)
  • 1
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    Resonance broadening measurements of atomic oxygen at 130nm (1998)
    Elsevier
    Details
    Publication Date: 1998-07-01
    Print ISSN: 0022-4073
    Electronic ISSN: 1879-1352
    Topics: Physics
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Atomic Resonance Radiation Energetics Investigation as a Diagnostic Method for Non-Equilibrium Hypervelocity Flows (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Absorption measurements with a tunable vacuum ultraviolet light source have been proposed as a concentration diagnostic for atomic oxygen, and the viability of this technique is assessed in light of recent measurements. The instrumentation, as well as initial calibration measurements, have been reported previously. We report here additional calibration measurements performed to study the resonance broadening line shape for atomic oxygen. The application of this diagnostic is evaluated by considering the range of suitable test conditions and requirements, and by identifying issues that remain to be addressed.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA-CR-200803 , NAS 1.26:200803
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    On Kinetics Modeling of Vibrational Energy Transfer (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.
    Keywords: Physics (General)
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Arcjets for Aerodynamic and Materials Testing: Flow Characterization (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Potential use of Arcjets as a hypersonic ground test facility for aerodynamic testing of future space vehicles is examined. Since high fidelity simulation of flight freestream conditions is a basic requirement for any useful ground test facility, it is imperative that the Arcjet flow field be thoroughly investigated in a systematic and orderly manner. At the same time we must know how and to what extent an inaccurate simulation of the flight freestream will effect the test data. The paper after discussing these two topics, describes various experimental techniques for Arcjet flow characterization. Results from an on-going Arcjet flow characterization program are also presented.
    Keywords: Research and Support Facilities (Air)
    Type: 34th AIAA Aerospace Sciences Meeting; Jan 01, 1996; Reno, NV; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    A Detailed Level Kinetics Model of NO Vibrational Energy Distributions (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Several contemporary problems have pointed to the desirability of a detailed level kinetics approach to modeling the distribution of vibrational energy in NO. Such a model is necessary when vibrational redistribution reactions are insufficient to maintain a Boltzmann distribution over the vibrational energy states. Recent calculations of the rate constant for the first reaction of the Zeldovich mechanism (N2 + O (goes to) NO + N) have suggested that the product NO is formed in high vibrational states. In shock layer flowfields, the product NO molecules may experience an insufficient number of collisions to establish a Boltzmann distribution over vibrational states, thus necessitating a level kinetics model. In other flows, such as expansions of high temperature air, fast, near-resonance vibrational energy exchanges with N2 and O2 may also require a level specific model for NO because of the relative rates of vibrational exchange and redistribution. The proposed report will integrate computational and experimental components to construct such a model for the NO molecule.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: AIAA 35th Aerospace Sciences Meeting and Exhibit; Jan 06, 1997 - Jan 09, 1997; Reno, NV; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Vibrational Energy Coupling in Expanding N2/O2/NO Admixtures (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Recent direct measurements of N2 and O2 vibrational populations in expansions of synthetic air show a closer coupling of the vibrational energies than indicated by adapting earlier experimental results from shock compressions to the nozzle expansion problem. An important difference between the shock wave and nozzle flow problems is the presence of NO in significant amounts throughout the relaxation in the case of a nozzle flow. This may account for the stronger coupling since NO is well suited to promote vibrational energy exchange. The results of a series of experiments and analysis examining vibrational energy coupling in expansions of admixtures approximating air are reported. N2 and O2 vibrational populations are determined by a single-pulse spontaneous Raman scattering technique. NO vibrational populations are determined by broadband absorption by the NO(y) system. The resulting data permit the role of NO in promoting vibrational energy coupling to be better understood, and are used to evaluate models of vibrational energy exchange for application to expanding flows.
    Keywords: Physics (General)
    Type: 31st AIAA Thermophysics Conference; Jun 17, 1996 - Jun 20, 1996; New Orleans, LA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Computations of Axisymmetric Flows in Hypersonic Shock Tubes (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A time-accurate two-dimensional fluid code is used to compute test times in shock tubes operated at supersonic speeds. Unlike previous studies, this investigation resolves the finer temporal details of the shock-tube flow by making use of modern supercomputers and state-of-the-art computational fluid dynamic solution techniques. The code, besides solving the time-dependent fluid equations, also accounts for the finite rate chemistry in the hypersonic environment. The flowfield solutions are used to estimate relevant shock-tube parameters for laminar flow, such as test times, and to predict density and velocity profiles. Boundary-layer parameters such as bar-delta(sub u), bar-delta(sup *), and bar-tau(sub w), and test time parameters such as bar-tau and particle time of flight t(sub f), are computed and compared with those evaluated by using Mirels' correlations. This article then discusses in detail the effects of flow nonuniformities on particle time-of-flight behind the normal shock and, consequently, on the interpretation of shock-tube data. This article concludes that for accurate interpretation of shock-tube data, a detailed analysis of flowfield parameters, using a computer code such as used in this study, must be performed.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA/TM-96-207282 , NAS 1.15:207282 , AIAA Paper 95-0713 , Aerospace Sciences Meeting and Exhibit; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States|Journal of Thermophysics and Heat Transfer; 10; 1; 169-176
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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