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  • ASTROPHYSICS  (2,970)
  • AERODYNAMICS  (2,091)
  • 1980-1984  (5,061)
  • 1
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    Multidomain approach for calculating compressible flows (1982)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A multidomain approach for calculating compressible flows by using unsteady or pseudo-unsteady methods is presented. This approach is based on a general technique of connecting together two domains in which hyperbolic systems (that may differ) are solved with the aid of compatibility relations associated with these systems. Some examples of this approach's application to calculating transonic flows in ideal fluids are shown, particularly the adjustment of shock waves. The approach is then applied to treating a shock/boundary layer interaction problem in a transonic channel.
    Keywords: AERODYNAMICS
    Type: NASA-TM-76692 , NAS 1.15:76692
    Format: application/pdf
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  • 2
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    Current developments lighter than air systems (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Lighter than air aircraft (LTA) developments and research in the United States and other countries are reviewed. The emphasis in the U.S. is on VTOL airships capable of heavy lift, and on long endurance types for coastal maritime patrol. Design concepts include hybrids which combine heavier than air and LTA components and characteristics. Research programs are concentrated on aerodynamics, flight dynamics, and control of hybrid types.
    Keywords: AERODYNAMICS
    Type: NASA-TM-84744 , NAS 1.15:84744
    Format: application/pdf
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  • 3
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    The 1979 X-ray outburst of Centaurus X-4 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: X-ray observations of the first major outburst of the classical transient X-ray source Centaurus X-4 since its discovery in 1969 are presented. The observations were obtained in May, 1979, with the all-sky monitor on board Ariel 5. The flare light curve is shown to exhibit many of the characteristics of other transients, including a double-peaked maximum, as well as significant, apparently random, variations and a lower peak flux and shorter duration than the 1969 event. Application of a standard epoch-folding technique to data corrected for linear decay trends indicates a possible source modulation at 0.3415 days (8.2 hours). Comparison of the results with previous other data on Cen X-4 and the characteristics of the soft X-ray transients allows a total X-ray output of approximately 3 x 10 to the 43rd ergs to be estimated, and reveals the duration and decay time of the 1979 Cen X-4 outburst to be the shortest yet observed from soft X-ray transients. The observations are explained in terms of episodic mass exchange from a late-type dwarf onto a neutron star companion in a relatively close binary system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
    Format: text
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  • 4
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    Experimental investigation of the flow on the suction side of a thin Delta wing (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Surface oil flow patterns were photographed and pressure distribution measurements were carried out on a sharp edged delta wing of aspect ratio lambda = 1.0 in order to determine the influence of Reynolds number and of vortex breakdown on the flow on the suction side of the wing. The formation of the secondary vortex occurs due to separation of a laminar boundary layer in the front part of the wing and due to separation of a turbulent boundary layer in the rear part of the wing. In the case of turbulent separation, the secondary separation line is closer to the wing leading edge than in the laminar case. The position of the transition depends on the Reynolds number and on the angle of incidence. The breakdown of a vortex above the wing leads to a kink in the secondary separation line.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75897
    Format: application/pdf
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  • 5
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    The influence of a high pressure gradient on unsteady velocity perturbations in the case of a turbulent supersonic flow (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The amplification or reduction of unsteady velocity perturbations under the influence of strong flow acceleration or deceleration was studied. Supersonic flows with large velocity, pressure gradients, and the conditions in which the velocity fluctuations depend on the action of the average gradients of pressure and velocity rather than turbulence, are described. Results are analyzed statistically and interpreted as a return to laminar process. It is shown that this return to laminar implies negative values in the turbulence production terms for kinetic energy. A simple geometrical representation of the Reynolds stress production is given.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75236 , AAF-NT-79-10 , Colloq. d''Aerodynamique Appl.; Nov 07, 1978 - Nov 09, 1978; Marseille; France|Jul 01, 1979
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  • 6
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    Evaluation of orbits with incomplete knowledge of the mathematical expectancy and the matrix of covariation of errors (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The problem of selecting the optimal algorithm of filtration and the optimal composition of the measurements is examined assuming that the precise values of the mathematical expectancy and the matrix of covariation of errors are unknown. It is demonstrated that the optimal algorithm of filtration may be utilized for making some parameters more precise (for example, the parameters of the gravitational fields) after preliminary determination of the elements of the orbit by a simpler method of processing (for example, the method of least squares).
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76237
    Format: application/pdf
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  • 7
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    Unsteady effects of a control surface in two dimensional subsonic and transonic flow (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The experimental results of steady and unsteady pressure measurements, carried out in subsonic and transonic flow on a 16 percent relative thickness supercritical aerofoil, equipped with a trailing edge flap involving 25 percent of the chord, in a sinusoidal motion are given. These experimental results are compared with those obtained by various methods of steady and unsteady inviscid flow calculations. Some calculation results in which viscous effects have been taken into account, for both steady and unsteady flows, are also presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75775 , AGARD-CP-262
    Format: application/pdf
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  • 8
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    Space superbubble 1200 light years across (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-NEWS-RELEASE-80-3 , P80-10003
    Format: application/pdf
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  • 9
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    On the swelling of rolled up vortex surfaces and the breakdown of the vortex core for slender wings (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Simplified models of the vortex distribution over cylindrical surfaces are developed. The effect of a change of vortex strength was analyzed quantitatively by menas of potential theory. The considerable bulging of the cylindrical vortex sheet as a consequence of the change of the vortex strength is discussed. The coiling-up of the vortices rotation in opposite directions over the cylindrical surface renders the condition for instability and the subsequent large spreading of the vortex core. These processes occur without a positive pressure gradient being necessary in the field of flow surrounding the coiled up vortex sheet.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75862
    Format: application/pdf
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  • 10
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    Nature of type 1 Supernovae (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The nature of type 1 supernovae (SN 1) is discussed through a comparison of observational evidence and theoretical perspectives relating to both type 1 and 2 supernovae. In particular two hypotheses relating to SN 1 phenomenon are examined: the first proposing that SN 1 are components of binary systems in which, at a comparatively late stage of evolution, overflow of the mass occurs; the second considers pre-SN 1 to be recently evolved stars with a mass greater than 1.4 solar mass (white dwarfs). In addition, an explanation of the reduced frequency of flares of SN 1 in spiral galaxies as related to that in elliptical galaxies is presented.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76238 , PR-395
    Format: application/pdf
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