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  • AERODYNAMICS  (83)
  • ENERGY PRODUCTION AND CONVERSION  (61)
  • METEOROLOGY AND CLIMATOLOGY
  • population models
  • 2020-2023
  • 1990-1994
  • 1980-1984
  • 1975-1979  (172)
  • 1970-1974
  • 1976  (172)
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Keywords
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  • 2020-2023
  • 1990-1994
  • 1980-1984
  • 1975-1979  (172)
  • 1970-1974
Year
  • 1
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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
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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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
  • 3
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    Aerodynamic heat transfer to a hypersonic research aircraft model /X-24C/ at Mach 6 (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The paper reports on results of heat-transfer tests conducted on a 1/29-scale model of the X-24C-12I hypersonic research aircraft configuration in a Mach 6 tunnel at a Reynolds number of thirteen million using the phase-change heat transfer technique. Sequences of phase-change heat transfer pattern photographs are presented showing windward side and leeward side heating processes. Theoretical predictions of dimensionless heat transfer coefficients along a data line on lower fuselage and on fuselage side bracket the experimental values. A turbulent heating theory gives good agreement with data when shifted to a new virtual origin.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; Dec. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Determination of statistics for any rotation of axes of a bivariate normal elliptical distribution (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Transformation of statistics from a dimensional set to another dimensional set involves linear functions of the original set of statistics. Similarly, linear functions will transform statistics within a dimensional set such that the new statistics are relevant to a new set of coordinate axes. A restricted case of the latter is the rotation of axes in a coordinate system involving any two correlated random variables. A special case is the transformation for horizontal wind distributions. Wind statistics are usually provided in terms of wind speed and direction (measured clockwise from north) or in east-west and north-south components. A direct application of this technique allows the determination of appropriate wind statistics parallel and normal to any preselected flight path of a space vehicle. Among the constraints for launching space vehicles are critical values selected from the distribution of the expected winds parallel to and normal to the flight path. These procedures are applied to space vehicle launches at Cape Kennedy, Florida.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology; 15; Feb. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Velocity surveys in a turbine stator annular-cascade facility using laser Doppler techniques (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A laser Doppler velocimeter (LDV) was used to determine the flow conditions downstream of an annular cascade of stator blades operating at an exit critical velocity ratio of 0.87. Two modes of LDV operation (continuous scan and discrete point) were investigated. Conventional pressure probe measurements were also made for comparison with the LDV results. Biasing errors that occur in the LDV measurement of velocity components were also studied. In addition, the effect of pressure probe blockage on the flow conditions was determined with the LDV. Photographs and descriptions of the test equipment used are given.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-8269 , E-8637
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Analysis and testing of two-dimensional vented Coanda ejectors with asymmetric variable area mixing sections (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The analysis of asymmetric, curved (Coanda) ejector flow has been completed using a finite difference technique and a quasi-orthogonal streamline coordinate system. The boundary layer type jet mixing analysis accounts for the effect of streamline curvature in pressure gradients normal to the streamlines and on eddy viscosities. The analysis assured perfect gases, free of pressure discontinuities and flow separation and treated three compound flows of supersonic and subsonic streams. Flow parameters and ejector performance were measured in a vented Coanda flow geometry for the verification of the computer analysis. A primary converging nozzle with a discharge geometry of 0.003175 m x 0.2032 m was supplied with 0.283 cu m/sec of air at about 241.3 KPa absolute stagnation pressure and 82 C stagnation temperature. One mixing section geometry was used with a 0.127 m constant radius Coanda surface. Eight tests were run at spacing between the Coanda surface and primary nozzle 0.01915 m and 0.318 m and at three angles of Coanda turning: 22.5 deg, 45.0 deg, and 75.0 deg. The wall static pressures, the loci of maximum stagnation pressures, and the stagnation pressure profiles agree well between analytical and experimental results.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2721
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    The plasmatron: Advanced mode thermionic energy conversion (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A theory of the plasmatron was developed. Also, a wide range of measurements were obtained with two versatile, research devices. To gain insight into plasmatron performance, the experimental results are compared with calculations based on the theoretical model of plasmatron operation. Results are presented which show that the plasma arc drop of the conventional arc (ignited) mode converter can be suppressed by use of an auxiliary ion source. The improved performance, however, is presently limited to low current densities because of voltage losses due to plasma resistance. This resistance loss could be suppressed by an increase in the plasma electron temperature or a decrease in spacing. Plasmatron performance characteristics for both argon and cesium are reported. The argon plasmatron has superior performance. Results are also presented for magnetic cutoff effects and for current distributing effects. These are shown to be important factors for the design of practical devices.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-135139 , NSR-5-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Analysis of information systems for hydropower operations: Executive summary (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analysis was performed of the operations of hydropower systems, with emphasis on water resource management, to determine how aerospace derived information system technologies can effectively increase energy output. Better utilization of water resources was sought through improved reservoir inflow forecasting based on use of hydrometeorologic information systems with new or improved sensors, satellite data relay systems, and use of advanced scheduling techniques for water release. Specific mechanisms for increased energy output were determined, principally the use of more timely and accurate short term (0-7 days) inflow information to reduce spillage caused by unanticipated dynamic high inflow events. The hydrometeorologic models used in predicting inflows were examined in detail to determine the sensitivity of inflow prediction accuracy to the many variables employed in the models, and the results were used to establish information system requirements. Sensor and data handling system capabilities were reviewed and compared to the requirements, and an improved information system concept was outlined.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-149342 , JPL-5040-43
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    A method to account for variation of average compressor inlet pressure during instantaneous distortion analyses (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Instantaneous distortion analyses compare a time-varying value of an index (or 'surge margin used up') with a critical level (or 'available surge margin' of the compressor) to determine inlet-engine compatibility. Unless freestream conditions or propulsion system controls are changing, it is generally assumed that the available surge margin of the compressor is accurately determined from the steady-state operating point. Results are presented which show that variations of average compressor inlet pressure may occur without changes in freestream conditions or propulsion system controls. The volume dynamics of the compressor will cause these pressure variations to be attenuated and delayed by the time they reach the exit. This will cause the compressor pressure ratio (and available surge margin) to vary with time. A method is presented to calculate the available surge margin as a function of time and incorporate it into an instantaneous distortion analysis. Results show that inlet pressure variations which cause only a small change at the compressor exit can cause a significant variation in the available surge margin.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 76-703 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    The plasmatron as an advanced performance thermionic converter (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A study concerned with the improvement of thermionic converter performance has shown that the plasma arc drop of the conventional arc (ignited) mode converter can be suppressed by use of an auxiliary ion source as in a plasmatron converter. However, this improved performance is now limited to low current densities and narrow interelectrode spacings because of voltage losses due to plasma resistance. An examination of plasmatron performance characteristics for both argon and cesium plasma has shown that the argon plasmatron is superior.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Conference on Intersociety Energy Conversion Engineering; Sep 12, 1976 - Sep 17, 1976; State Line, NV
    Format: text
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    NASA TECHNICAL REPORTS
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