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  • 1
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    Entropy effects and shock fitting in conical supersonic full potential flows (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 461-49
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Supersonic full-potential method applied to missile bodies (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The NCOREL full-potential method with an entropy correction is presently applied to supersonic missile flowfield problems. After defining the salient characteristics of the method, a combination of linear theory with NCOREL and experimental data is used to isolate the nonlinear features of the supersonic flow so that the influence of geometry and flow conditions on the development of such flow nonlinearities can be appreciated. Comparisons of experimental longitudinal force and moment data with NCOREL and various linear theory predictions are presented for several generic missile airframe configurations of circular and elliptic cross section. The NCOREL code solves the nonconservative full potential equation in a spherical coordinate system; exact boundary conditions are defined on the missile surface.
    Keywords: AERODYNAMICS
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    NASA TECHNICAL REPORTS
  • 3
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    Nonlinear aerodynamic effects on bodies in supersonic flow (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 21; 809-815
    Format: text
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  • 4
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    Ground signature extrapolation of three-dimensional near-field CFD predictions for several HSCT configurations (1992)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A CFD analysis of the near-field sonic boom environment of several low boom High Speed Civilian Transport (HSCT) concepts is presented. The CFD method utilizes a multi-block Euler marching code within the context of an innovative mesh topology that allows for the resolution of shock waves several body lengths from the aircraft. Three-dimensional pressure footprints at one body length below three-different low boom aircraft concepts are presented. Models of two concepts designed by NASA to cruise at Mach 2 and Mach 3 were built and tested in the wind tunnel. The third concept was designed by Boeing to cruise at Mach 1.7. Centerline and sideline samples of these footprints are then extrapolated to the ground using a linear waveform parameter method to estimate the ground signatures or sonic boom ground overpressure levels. The Mach 2 concept achieved its centerline design signature but indicated higher sideline booms due to the outboard wing crank of the configuration. Nacelles are also included on two of NASA's low boom concepts. Computations are carried out for both flow-through nacelles and nacelles with engine exhaust simulation. The flow-through nacelles with the assumption of zero spillage and zero inlet lip radius showed very little effect on the sonic boom signatures. On the other hand, it was shown that the engine exhaust plumes can have an effect on the levels of overpressure reaching the ground depending on the engine operating conditions. The results of this study indicate that engine integration into a low boom design should be given some attention.
    Keywords: ACOUSTICS
    Type: NASA. Langley Research Center, High-Speed Research: Sonic Boom, Volume 2; p 175-200
    Format: application/pdf
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  • 5
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    Application of NCOREL to aircraft configurations (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The NCOREL computer program and methodology (Grossman, 1979) modified for computation of flows over complex geometries is described. The newly introduced features include a more flexible grid-generation package, capable of generating grids for realistic wing-body cross sections, and a more general numerical method, developed for the capture of highly three-dimensional embedded, oblique shocks. In addition, an inlet capability is included, by means of which the cross section is allowed to change discontinuously with the addition of the inlet geometry. The new cross section is regridded and the potentials and their derivatives are interpolated for the marching to continue. Hence, a discontinuity in the grid or mappings is taken into account at the inlet station. The results of the flow-field computation for a realistic fighter configuration are discussed.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 86-1830
    Format: text
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  • 6
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    Application of NCOREL to conical multi-finned and multi-faceted configurations (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A more versatile analytic conformal mapping approach for grid generation is implemented in a full potential supersonic flow code (NCOREL). Configurations such as multi-finned bodies and wings with vertical tails cannot be treated using a single conformal mapping transformation for grid generation. Instead, a series of analytic conformal mappings are used in progression to generate grids that are capable of resolving the complex multiple shock flow fields that exist about these configurations. Aplications of the grid generation techniques are presented for a variety of cross sections along with their conical full potential flow solutions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-0441
    Format: text
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  • 7
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    An Euler code prediction of near field to midfield sonic boom pressure signatures (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A new approach is presented for computing sonic boom pressure signatures in the near field to midfield that utilizes a fully three-dimensional Euler finite volume code capable of analyzing complex geometries. Both linear and nonlinear sonic boom methodologies exist but for the most part rely primarily on equivalent area distributions for the prediction of far field pressure signatures. This is due to the absence of a flexible nonlinear methodology that can predict near field pressure signatures generated by three-dimensional aircraft geometries. It is the intention of the present study to present a nonlinear Euler method than can fill this gap and supply the needed near field signature data for many of the existing sonic boom codes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 90-4000
    Format: text
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  • 8
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    Computation of nonlinear supersonic potential flow over three-dimensional surfaces (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 12, p. 1850, Accession no. A82-27090
    Keywords: AERODYNAMICS
    Type: (ISSN 0021-8669)
    Format: text
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  • 9
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    Nonlinear aerodynamic effects on bodies in supersonic flow (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The supersonic flow about generic bodies was analyzed to identify the elments of the nonlinear flow and to determine the influence of geometry and flow conditions on the magnitude of these nonlinearities. The nonlinear effects were attributed to separated-flow nonlinearities and attached-flow nonlinearities. The nonlinear attached-flow contribution was further broken down into large-disturbance effects and entropy effects. Conical, attached-flow bundaries were developed to illustrate the flow regimes where the nonlinear effects are significant, and the use of these boundaries for angle of attack and three-dimensional geometries was indicated. Normal-force and pressure comparisons showed that the large-disturbance and separated-flow effects were the dominant nonlinear effects at low supersonic Mach numbers and that the entropy effects were dominant for high supersonic Mach number flow. The magnitude of all the nonlinear effects increased with increasing angle of attack. A full-potential method, NCOREL, which includes an approximate entropy correction, was shown to provide accurate attached-flow pressure estimates from Mach 1.6 through 4.6.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-0231
    Format: text
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  • 10
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    Study of VTOL in ground-effect flow field including temperature effect (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Detailed pressure, temperature, and velocity data were obtained for twin-fan configurations in-ground-effect and flow models to aid in predicting pressures and upwash forces on aircraft surfaces were developed. For the basic experiments, 49.5 mm-diameter jets were used, oriented normal to a simulated round plane, with pressurized, heated air providing a jet. The experimental data consisted of: (1) the effect of jet height and temperature on the ground, model, and upwash pressures, and temperatures, (2) the effect of simulated aircraft surfaces on the isolated flow field, (3) the jet-induced forces on a three-dimensional body with various strakes, (4) the effects of non-uniform coannular jets. For the uniform circular jets, temperature was varied from room temperature (24 C) to 232 C. Jet total pressure was varied between 9,300 Pascals and 31,500 Pascals. For the coannular jets, intended to represent turbofan engines, fan temperature was maintained at room temperature while core temperature was varied from room temperature to 437 C. Results are presented.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-CR-166258 , NAS 1.26:166258
    Format: application/pdf
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