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  • Other Sources  (189)
  • AERODYNAMICS  (83)
  • METEOROLOGY AND CLIMATOLOGY  (63)
  • AIRCRAFT PROPULSION AND POWER  (43)
  • Cell & Developmental Biology
  • 1980-1984  (189)
  • 1955-1959
  • 1935-1939
  • 1980  (189)
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  • 1980-1984  (189)
  • 1955-1959
  • 1935-1939
Year
  • 1
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    Eddy diffusion coefficients and the variance of the atmosphere 30-60 km (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The results of numerical models or of new observational programs are checked by comparing them with past observations. In view of the differing analysis techniques or differing data samples, the eddy diffusivities presented here agree remarkably well with past estimates. However, in the application of K-values to two-dimensional models, the actual magnitude of the diffusivities is no more important than their spatial patterns, i.e., their gradients with height and latitude. It should thus be noted that the present patterns are often much different from those of past results.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Pure and Applied Geophysics; 118; 5, 19; 1980
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Determination of the complex refractive index and size distribution of atmospheric particulates from bistatic-monostatic lidar and solar radiometer measurements (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A method is presented for inferring both the size distribution and the complex refractive index of atmospheric particulates from combined bistatic-monostatic lidar and solar radiometer observations. The basic input measurements are spectral optical depths at several visible and near-infrared wavelengths as obtained with a solar radiometer and backscatter and angular scatter coefficients as obtained from a biostatic-monostatic lidar. The spectral optical depth measurements obtained from the radiometer are mathematically inverted to infer a columnar particulate size distribution. Advantage is taken of the fact that the shape of the size distribution obtained by inverting the particulate optical depth is relatively insensitive to the particle refractive index assumed in the inversion. Bistatic-monostatic angular scatter and backscatter lidar data are then processed to extract an optimum value for the particle refractive index subject to the constraint that the shape of the particulate size distribution be the same as that inferred from the solar radiometer data. Specifically, the scattering parameters obtained from the bistatic-monostatic lidar data are compared with corresponding theoretical computations made for various assumed refractive index values. That value which yields best agreement, in a weighted least squares sense, is selected as the optimal refractive index estimate. The results of this procedure applied to a set of simulated measurements as well as to measurements collected on two separate days are presented and discussed.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research; 85; Mar. 20
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    NASA TECHNICAL REPORTS
  • 3
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    A computational and experimental study of high Reynolds number viscous/inviscid interaction about a cone at high angle of attack (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The flow over a 5 deg semi-angle cone at incidence in supersonic flow is studied as a model problem for the flow over aircraft forebodies. A computational method utilizing the conically symmetric Navier-Stokes equations is used to obtain theoretical flow results which are compared with experimental data from the Ames Research Center 6- by 6-Foot Wind Tunnel and with results from a cone model sting mounted on an F-15 aircraft. The computed results agree well with the wind-tunnel data but less well with the flight data. Modification of the algebraic turbulence model was necessary to reflect an apparent lower turbulence level in flight than was present in the wind tunnel.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-1422 , Fluid and Plasma Dynamics Conference; Jul 14, 1980 - Jul 16, 1980; Snowmass, CO
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  • 4
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    Preparing aircraft propulsion for a new era in energy and the environment (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Improving fuel efficiency, new sources of jet fuel, and noise and emission control are subjects of NASA's aeronautics program. Projects aimed at attaining a 5% fuel savings for existing engines and a 13-22% savings for the next generation of turbofan engines using advanced components, and establishing a basis for turboprop-powered commercial air transports with 30-40% savings over conventional turbofan aircraft at comparable speeds and altitudes, are discussed. Fuel sources are considered in terms of reduced hydrogen and higher aromatic contents and resultant higher liner temperatures, and attention is given to lean burning, improved fuel atomization, higher freezing-point fuel, and deriving jet fuel from shale oil or coal. Noise sources including the fan, turbine, combustion process, and flow over internal struts, and attenuation using acoustic treatment, are discussed, while near-term reduction of polluting gaseous emissions at both low and high power, and far-term defining of the minimum gaseous-pollutant levels possible from turbine engines are also under study.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Astronautics and Aeronautics; 18; Jan. 198
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  • 5
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    Unsteady transonic small disturbance theory with strong shock waves (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A theory to correct the transonic small disturbance (TSD) equation to treat strong shock waves in unsteady flow is developed. The technique involves the addition of higher order terms, which are formally of negligible magnitude, to the low frequency TSD equation. These terms are then chosen such that any shock waves in the flow have strengths approximately equal to the appropriate Rankine-Hugoniot shock strength. Two correcting approaches are investigated. The first is to derive a correction for the mean steady flow and then simply use this corrected form for oscillatory flows. The second is to derive a correction for both steady and oscillatory parts of the flow. This second development is the most satisfactory and comparisons of the present results with Euler equation results are generally favorable, particularly regarding shock location, although there are some discrepancies in the pressure distribution in the leading edge region.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166157 , NEAR-TR-230
    Format: application/pdf
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  • 6
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    Propulsion Study for Small Transport Aircraft Technology (STAT) (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Propulsion requirements were determined for 0.5 and 0.7 Mach aircraft. Sensitivity studies were conducted on both these aircraft to determine parametrically the influence of propulsion characteristics on aircraft size and direct operating cost (DOC). Candidate technology elements and design features were identified and parametric studies conducted to select the STAT advanced engine cycle. Trade off studies were conducted to determine those advanced technologies and design features that would offer a reduction in DOC for operation of the STAT engines. These features were incorporated in the two STAT engines. A benefit assessment was conducted comparing the STAT engines to current technology engines of the same power and to 1985 derivatives of the current technology engines. Research and development programs were recommended as part of an overall technology development plan to ensure that full commercial development of the STAT engines could be initiated in 1988.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165499 , DDA-EDR-10470
    Format: application/pdf
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  • 7
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    Numerical lifting line theory applied to drooped leading-edge wings below and above stall (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A numerical iterative solution to the classical Prandtl lifting-line theory, suitably modified for poststall behavior, is used to study the aerodynamic characteristics of straight rectangular finite wings with and without leading-edge droop. This study is prompted by the use of such leading-edge modifications to inhibit stall/spins in light general aviation aircraft. The results indicate that lifting-line solutions at high angle of attack can be obtained that agree with experimental data to within 20%, and much closer for many cases. Therefore, such solutions give reasonable preliminary engineering results for both drooped and undrooped wings in the poststall region. However, as predicted by von Karman, the lifting-line solutions are not unique when sectional negative lift slopes are encountered. In addition, the present numerical results always yield symmetrical lift distributions along the span, in contrast to the asymmetrical solutions observed by Schairer in the late 1930's. Finally, a series of parametric tests at low angle of attack indicate that the effect of drooped leading edges on aircraft cruise performance is minimal.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 17; Dec. 198
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  • 8
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    Estimating probabilities of cloud-free fields-of-view from the earth through the atmosphere (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper is an extension of previous papers by Lund and Shanklin (1972, 1973). It presents probabilities of cloud-free fields-of-view (CFFOV) to supplement probabilities of cloud-free lines-of-sight (CFLOS) contained in the earlier papers. A model is developed for estimating the probability of obtaining a CFFOV as a function of ground-observer-reported total sky cover for earth-to-space applications. The development of the model and examples of its application are described. A comparison of CFFOV and CFLOS results is made. In conclusion, climatic probabilities of CFFOV overhead through the entire atmosphere between the surface of the earth and space can be estimated for any desired geographical location through the use of a specified equation and conditional probabilities contained in the paper, if the frequency distribution of total sky cover categories for the desired location is known.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: AD-A086320 , AFGL-TR-80-0183 , Journal of Applied Meteorology; 19; Apr. 198
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Combined linear theory/impact theory method for analysis and design of high speed configurations (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Pressure distributions on a wing body at Mach 4.63 are calculated. The combined theory is shown to give improved predictions over either linear theory or impact theory alone. The combined theory is also applied in the inverse design mode to calculate optimum camber slopes at Mach 4.63. Comparisons with optimum camber slopes obtained from unmodified linear theory show large differences. Analysis of the results indicate that the combined theory correctly predicts the effect of thickness on the loading distributions at high Mach numbers, and that finite thickness wings optimized at high Mach numbers using unmodified linear theory will not achieve the minimum drag characteristics for which they are designed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3314
    Format: application/pdf
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  • 10
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    A flight investigation of blade section aerodynamics for a helicopter main rotor having NLR-1T airfoil sections (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A flight investigation was conducted using a teetering-rotor AH-1G helicopter to obtain data on the aerodynamic behavior of main-rotor blades with the NLR-1T blade section. The data system recorded blade-section aerodynamic pressures at 90 percent rotor radius as well as vehicle flight state, performance, and loads. The test envelope included hover, forward flight, and collective-fixed maneuvers. Data were obtained on apparent blade-vortex interactions, negative lift on the advancing blade in high-speed flight and wake interactions in hover. In many cases, good agreement was achieved between chordwise pressure distributions predicted by airfoil theory and flight data with no apparent indications of blade-vortex interactions.
    Keywords: AERODYNAMICS
    Type: NASA-TM-80166 , AVRADCOM-TR-80-B-2
    Format: application/pdf
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