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  • AERODYNAMICS  (448)
  • ASTROPHYSICS  (418)
  • FLUID MECHANICS AND HEAT TRANSFER  (180)
  • GENERAL
  • 1975-1979  (1,046)
  • 1955-1959  (31)
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  • 1
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    A comparison of the Method of Lines to finite difference techniques in solving time-dependent partial differential equations (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computers and Fluids; 6; June 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    The radiation history of material returned by the Soviet automatic stations Luna 16 and Luna 20, according to track studies (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Fission tracks formed by the vH (very heavy) nuclei group of solar and galactic cosmic rays have been studied in silicate minerals of the lunar regolith returned by the Luna 16 and Luna 20 unmanned spacecraft. It is shown that the material in the Luna 16 core sample, from a typical mare region of the lunar surface, has undergone stronger irradiation by cosmic rays than material returned a highland region by Luna 20. A low-irradiation component (about 10 percent of the total number of crystals) has been found in the Luna 20 core sample materials, which can possibly be attributed to material added to the main bulk of the regolith in the formation of the crater Apollonius C. From the track density distribution of crystals, as a function of depth in the regolith core sample, it follows that the process of formation of the upper layer of the regolith, both for the lunar mare and for the highland region, includes sequential layering of finely crushed crystalline matter and subsequent mixing of it by micrometeorite bombardment. A portion of the crystals with a very high track density may be a component added to the lunar surface from outer space.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, Pt. 2; p 745-754
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Aerodynamic characteristics in ground proximity (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results from recent investigations in the Langley V/STOL tunnel of an externally blown flap and an upper surface blown flap configuration in ground proximity are presented. Comparisons of longitudinal aerodynamic characteristics indicate that in ground proximity, drag is reduced for both configurations, but changes in lift are configuration dependent. Steady state analyses of the landing approach indicate an increase in flight path angle for both configurations in ground proximity because of the drag reduction. Dynamic analyses with a fixed-base simulator indicate that the resultant flight path during landing approach is dependent on the initial flight path angle and the control technique used.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 145-158
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    NASA TECHNICAL REPORTS
  • 4
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    Investigation of the composition of the Luna 16 lunar sample (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The concentrations of aluminum, manganese, sodium, chromium, iron, cobalt, and 12 rare earth elements were determined by neutron activation analysis using slow neutrons. Oxygen and silicon were determined using a fast neutron generator. Mossbauer spectroscopy was used to investigate iron compounds in Luna 16 regolith samples from the upper part of the core.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, pt. 1; p 277-280
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    NASA TECHNICAL REPORTS
  • 5
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    Stellar model chromospheres. XI - A survey of Ca II lambda 8542 line profiles in late-type stars of differing chromospheric activity (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: PB80-144215 , Astrophysical Journal Supplement Series; 41; Nov. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Evaluation of a large capacity heat pump concept for active cooling of hypersonic aircraft structure (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of engineering analyses assessing the conceptual feasibility of a large capacity heat pump for enhancing active cooling of hypersonic aircraft structure are presented. A unique heat pump arrangement which permits cooling the structure of a Mach 6 transport to aluminum temperatures without the aid of thermal shielding is described. The selected concept is compatible with the use of conventional refrigerants, with Freon R-11 selected as the preferred refrigerant. Condenser temperatures were limited to levels compatible with the use of conventional refrigerants by incorporating a unique multipass condenser design, which extracts mechanical energy from the hydrogen fuel, prior to each subsequent pass through the condenser. Results show that it is technically feasible to use a large capacity heat pump in lieu of external shielding. Additional analyses are required to optimally apply this concept.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-145301
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    NASA TECHNICAL REPORTS
  • 7
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    An experimental and computational investigation of the flow field about a transonic airfoil in supercritical flow with turbulent boundary-layer separation (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A combined experimental and computational research program is described for testing and guiding turbulence modeling within regions of separation induced by shock waves incident in turbulent boundary layers. Specifically, studies are made of the separated flow the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include highfrequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-X-73157 , A-6690
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Steady and unsteady transonic flow (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An investigation of the transonic flow over a circular arc airfoil was conducted to obtain basic information for turbulence modeling of shock-induced separated flows and to verify numerical computer codes which are being developed to simulate such flows. The investigation included the employment of a laser velocimeter to obtain data concerning the mean velocity, the shear stress, and the turbulent kinetic energy profiles in the flowfield downstream of the airfoil midchord where the flow features are more complex. Depending on the free-stream Mach number, the flowfield developed was either steady with shock-wave-induced separation extending from the foot of the shock wave to beyond the trailing edge or unsteady with a periodic motion also undergoing shock-induced separation. The experimental data were compared with the results of numerical simulations in which a computer code was employed that solved the time-dependent Reynolds' averaged compressible Navier-Stokes equations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 78-160 , Aerospace Sciences Meeting; Jan 16, 1978 - Jan 18, 1978; Huntsville, AL
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    NASA TECHNICAL REPORTS
  • 9
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    An experimental and computational investigation of the flow field about a transonic airfoil in supercritical flow with turbulent boundary-layer separation (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A combined experimental and computational research program for testing and guiding turbulence modeling within regions of separation induced by shock waves incident on turbulent boundary layers is described. Specifically, studies are made of the separated flow over the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include high-frequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.
    Keywords: AERODYNAMICS
    Type: ICAS PAPER 76-15 , Congress; Oct 03, 1976 - Oct 08, 1976; Ottawa; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Aerodynamic drag reduction tests on a full-scale tractor-trailer combination and a representative box-shaped ground vehicle (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Keywords: AERODYNAMICS
    Type: SAE PAPER 750703 , West Coast Meeting; Aug 11, 1975 - Aug 14, 1975; Seattle, WA
    Format: text
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    NASA TECHNICAL REPORTS
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