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  • 11
    Publication Date: 2019-06-28
    Description: An experiment was performed on a low-aspect ratio wing to define the limits of the validity of codes which are used to predict the flow over modern fighter configurations. The focus of the experiment is to provide data at or near the true operating conditions of transonic aircraft. The Reynolds numbers reached in this experiment reproduce those experienced by an aircraft with a 5-m root chord, flying at 14 to 16 km, from Mach 0.6 to 0.8. The angle-of-attack range of the experiment extends into the regime of leading-edge separation.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-0402
    Format: text
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  • 12
    Publication Date: 2019-06-28
    Description: Hypersonic flow over spherical dome protuberances was investigated to determine increased pressure and heating loads to the surface. The configuration was mathematically modeled in a time-dependant three-dimensional analysis of the conservation of mass, momentum (Navier-Stokes), and energy equations. A boundary mapping techique was used to obtain a rectangular parallelepiped computational domain, and a MacCormack explicit time-split predictor-corrector finite difference algorithm was used to obtain solutions. Results show local pressures and heating rates for domes one-half, one, and two boundary layer thicknesses high were increased by factors on the order of 1.4, 2, and 6, respectively. However, because lee-side pressure and thermal loads were reduced the two lower height domes did not experience any net increase in total loads. The total loads on the higher dome were increased by twenty-five percent. Flow over the lower dome was everywhere attached while flow over the intermediate dome had small windward and leeside separations. The higher dome had an unsteady windward separation region and a large leeside separation region. Trailing vortices form on all domes with intensity increasing with dome height. Discussions of applying the results to a thermally bowed thermal protection system are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 83-1557
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  • 13
    Publication Date: 2019-06-27
    Description: Noise tests were conducted on a small-scale model of an externally blown flap lift augmentation system. The nozzle/wing model was subjected to external flow that simulated takeoff and landing flight velocities by placing it in a 33-centimeter-diameter free jet. The results showed that external flow attenuated the noise associated with the various configurations tested. The amount of attenuation depended on flap setting. More attenuation occurred with a trailing-flap setting of 20 deg than with one of 60 deg. Noise varied with relative velocity as a function of the trailing-flap setting and the angle from the nozzle inlet.
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-8305 , E-8697
    Format: application/pdf
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  • 14
    Publication Date: 2019-06-28
    Description: Attention is given to hypersonic laminar flow over a quilted surface configuration that simulates an array of Space Shuttle Thermal Protection System panels bowed in a spherical shape as a result of thermal gradients through the panel thickness. Pressure and heating loads to the surface are determined. The flow field over the configuration was mathematically modeled by means of time-dependent, three-dimensional conservation of mass, momentum, and energy equations. A boundary mapping technique was then used to obtain a rectangular, parallelepiped computational domain, and an explicit MacCormack (1972) explicit time-split predictor-corrector finite difference algorithm was used to obtain steady state solutions. Total integrated heating loads vary linearly with bowed height when this value does not exceed the local boundary layer thickness.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-1630
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  • 15
    Publication Date: 2019-07-13
    Description: Noise spectra were measured in three dimensions for several surfaces immersed in turbulent flow from a jet and over a range of flow conditions. The data are free field and were corrected to remove the small contributions of jet noise, atmospheric attenuation and feedback tones. These broadband data were compared with the results of available theories which are only strictly applicable to simple geometries over a limited range of conditions. The available theories proved to be accurate over the range of flow, chord length, thickness, angle of attack, and surface geometries defined by the experiments. These results apply to the noise generated by fixed surfaces in engine passages, the lifting surfaces of aircraft and also to fan noise.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 76-504 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 16
    Publication Date: 2019-07-13
    Description: Flow separation from nozzle surfaces can be a source of significant noise in addition to the jet noise. When no flow separation region exists only jet noise is observed at every angle, for velocities down to 120 m/sec, with both low and high levels of initial turbulence. Intense nearly periodic turbulence and noise is caused by flow separation from the thin core nozzle lip of a coaxial nozzle. This can be described by a combination of aeolian tone and trailing edge noise theory. Noise caused by flow separation from the surfaces of other nozzle geometries has somewhat different characteristics.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 76-3 , Aerospace Sciences Meeting; Jan 26, 1976 - Jan 28, 1976; Washington, DC
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  • 17
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Noise data with models of both internally and externally blown jet flaps designed for STOL aircraft
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-67850 , E-6355
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  • 18
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: Noise data were obtained with a large externally blown flap model. A fan-jet engine exhaust was simulated by a 1/2-scale bypass nozzle supplied by pressurized air. The nozzle was pylon mounted on a wing section having a double-slotted flap for lift augmentation. Noise radiation patterns and spectra were obtained for nozzle exhaust velocities between 400 and 1150 ft/sec. The blown flap noise data are in good agreement with previous small model results extrapolated to test conditions by Strouhal scaling. The results indicate that blown flap noise must be suppressed to meet STOL aircraft noise goals.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 72-129 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 17, 1972 - Jan 19, 1972; San Diego, CA
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  • 19
    Publication Date: 2019-07-13
    Description: Far field noise data were taken for convergent nozzles of various shapes and sizes at subsonic velocities exceeding 400 ft/sec. For a circular nozzle, the nozzle inlet shape and lip thickness had no effect on the noise level, directivity, or spectra when compared at the same nozzle exit diameter and peak exhaust velocity. A sharp edged orifice was one exception to this statement. Coannular nozzles can produce additional high frequency noise. Blunt ended centerbodies, where there is significant base drag, also generate significant additional noise.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 73-187 , Aerospace Sciences Meeting; Jan 10, 1973 - Jan 12, 1973; Washington, DC
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  • 20
    Publication Date: 2019-07-13
    Description: Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diam.) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 74-43 , Aerospace Sciences Meeting; Jan 30, 1974 - Feb 01, 1974; Washington, DC
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