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  • AERODYNAMICS  (867)
  • GENERAL
  • 1980-1984  (428)
  • 1975-1979  (448)
  • 1955-1959  (31)
  • 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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    Results of a low-speed wind tunnel test of the MDC 2.2M supersonic cruise aircraft configuration (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of a low speed test conducted in the Full Scale Tunnel at NASA Langley using an advanced supersonic cruise vehicle configuration are presented. These tests used a 10 percent scale model of a configuration that had demonstrated high aerodynamic performance at Mach 2.2 during a previous test program. The low speed model has leading and trailing edge flaps designed to improve low speed lift to drag ratios at high lift and includes devices for longitudinal and lateral/directional control. The results obtained during the low speed test program have shown that full span leading edge flaps are required for maximum performance. The amount of deflection of the leading edge flap must increase with C sub L to obtain the maximum benefit. Over 80 percent of full leading edge suction was obtained up to lift off C sub L's of 0.65. A mild pitch up occurred at about 6 deg angle of attack with and without the leading edge flap deflected. The pitch up is controllable with the horizontal tail. Spoilers were found to be preferable to spoiler/deflectors at low speeds. The vertical tail maintained effectiveness up to the highest angle of attack tested but the tail on directional stability deteriorated at high angles of attack. Lateral control was adequate for landing at 72 m/sec in a 15.4 m/sec crosswind.
    Keywords: AERODYNAMICS
    Type: Supersonic Cruise Res. 1979, Pt. 1; p 35-57
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    PAN AIR modeling studies (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: PAN AIR is a computer program that predicts subsonic or supersonic linear potential flow about arbitrary configurations. The code's versatility and generality afford numerous possibilities for modeling flow problems. Although this generality provides great flexibility, it also means that studies are required to establish the dos and don'ts of modeling. The purpose of this paper is to describe and evaluate a variety of methods for modeling flows with PAN AIR. The areas discussed are effects of panel density, internal flow modeling, forebody modeling in subsonic flow, propeller slipstream modeling, effect of wake length, wing-tail-wake interaction, effect of trailing-edge paneling on the Kutta condition, well- and ill-posed boundary-value problems, and induced-drag calculations. These nine topics address problems that are of practical interest to the users of PAN AIR.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 83-1830
    Format: text
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  • 4
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    PAN AIR prediction of NASA Ames 12-foot pressure wind-tunnel interference on a fighter configuration (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Models tested in the NASA Ames 12-Foot Pressure Wind Tunnel over an angle of attack range from 0 deg to 90 deg are mounted on a floor strut that protrudes from a fairly large support bump. In high-angle-of-attack tests (angle of attack = 40 deg to 90 deg), for which the floor support was originally designed, the effects of the flow angularities produced by the bump are often negligible. This is not so for low-angle-of-attack tests (0 deg to 40 deg). Since there are no standard means for correcting test data for this bump effect, low-angle-of-attack testing with the bump is not recommended by the Ames wind-tunnel staff. This paper presents an exploratory study of a technique for correcting balance forces and experimental pressures for combined wall and bump effects. This is done by modeling the aircraft, wind-tunngl walls, and bump, with PAN AIR. The wall-and-bump-induced increments in the lift coefficient and pitching-moment coefficient predicted by PAN AIR are compared with increments obtained from the Ames 12-foot tunnel with the bump and an 8 x 12 low speed wind tunnel which has no bump.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-0219
    Format: text
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  • 5
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    Low-frequency pressure fluctuations in axisymmetric turbulent boundary layers (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Measurements were made of wall pressure fluctuations under a turbulent boundary layer on the fuselage of a sailplane. Experiments with the sailplane offered a noise-free flow with a low free-stream turbulence level. In this environment the wall-pressure spectrum of a turbulent boundary layer with natural transition was found to drop off at low frequencies. Correlations between several wall-mounted microphones revealed that the large-scale motions contribute about 35% to the mean square pressure. Velocity fluctuations at several positions within and outside the boundary layer were measured and correlated with the wall pressure. It seems that the irrotational motions in the turbulent region are primarily responsible for the large-scale wall-pressure fluctuations. A time-lagged conditional correlation of the pressure was introduced to gain further insight into the pressure-producing motions.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 97; Mar. 25
    Format: text
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  • 6
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    Preflight reentry heat transfer analysis of Space Shuttle (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Preflight predictions of the structural temperature distributions during entry are compared with data from the initial Shuttle flight. Finite element thermal analysis programming was used to model the heat flow on Shuttle structures and actual gas properties of air were employed in the analyses of aerodynamic heating. Laminar, separated, and turbulent heat fluxes were calculated for varying locations on the craft using velocity-attitude and angle-of-attack projections taken from the nominal STS-1 trajectory. Temperature time histories of the first flight are compared with laminar and turbulent flow assumptions and an unpredicted rapid cooling 1800 sec into entry is credited to inaccurate assumptions of structural heat dissipative properties or flow conditions in that time phase of the flight; additional discrepancies in descriptions of heating of the upper fuselage are attributed to a lack of knowledge of the complex flow patterns existing over that area of the Shuttle body.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-2382 , Flight Testing Conference; Nov 11, 1981 - Nov 13, 1981; Las Vegas, NV
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Steady and unsteady transonic flow (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An investigation of the transonic flow over a circular arc airfoil was conducted to obtain basic information for turbulence modeling of shock-induced separated flows and to verify numerical computer codes which are being developed to simulate such flows. The investigation included the employment of a laser velocimeter to obtain data concerning the mean velocity, the shear stress, and the turbulent kinetic energy profiles in the flowfield downstream of the airfoil midchord where the flow features are more complex. Depending on the free-stream Mach number, the flowfield developed was either steady with shock-wave-induced separation extending from the foot of the shock wave to beyond the trailing edge or unsteady with a periodic motion also undergoing shock-induced separation. The experimental data were compared with the results of numerical simulations in which a computer code was employed that solved the time-dependent Reynolds' averaged compressible Navier-Stokes equations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 78-160 , Aerospace Sciences Meeting; Jan 16, 1978 - Jan 18, 1978; Huntsville, AL
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    NASA TECHNICAL REPORTS
  • 8
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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
  • 9
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    PAN AIR - A higher order panel method for predicting subsonic or supersonic linear potential flows about arbitrary configurations (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: PAN AIR is a computer program for predicting subsonic or supersonic linear potential flow about arbitrary configurations. It uses linear source and quadratic doublet strength distributions. These higher-order distributions have been implemented in a manner that greatly reduces the numerical stability problems that have plagued earlier attempts to make surface paneling methods work successfully for supersonic flow. PAN AIR's problem-solving capability, numerical approach, modeling features, and program architecture are described. Numerical results are presented for a variety of geometries at supersonic Mach numbers.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 81-1255 , Fluid and Plasma Dynamics Conference; Jun 23, 1981 - Jun 25, 1981; Palo Alto, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Boundary layer stability analysis of a natural laminar flow glove on the F-111 TACT airplane (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A natural laminar flow airfoil has been developed as a part of the aircraft energy efficiency program. A NASA flight program incorporating this airfoil into partial wing gloves on the F-111 TACT airplane was scheduled to start in May, 1980. In support of this research effort, an extensive boundary layer stability analysis of the partial glove has been conducted. The results of that analysis show the expected effects of wing leading-edge sweep angle, Reynolds number, and compressibility on boundary layer stability and transition. These results indicate that it should be possible to attain on the order of 60% laminar flow on the upper surface and 50% laminar flow on the lower surface for sweep angles of at least 20 deg, chord Reynolds numbers of 25 x 10 to the 6th and Mach numbers from 0.81 to 0.85.
    Keywords: AERODYNAMICS
    Type: Symposium on Viscous flow drag reduction; Nov 07, 1979 - Nov 08, 1979; Dallas, TX
    Format: text
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