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  • AERODYNAMICS  (114)
  • 2020-2024
  • 2010-2014
  • 1980-1984  (114)
  • 1970-1974
  • 1945-1949
  • 1980  (114)
  • 1
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    Zero-length, slotted-lip inlet for subsonic military aircraft (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Zero-length, slotted-lip inlet performance and associated fan blade stresses were determined during model tests using a 20-inch diameter fan simulator in the NASA-LeRC 9- by 15-foot low-speed wind tunnel. The model configuration variables consisted of inlet contraction ratio, slot width, circumferential extent of slot fillers, and length of a constant area section between the inlet throat and fan face. Inlet configurations having contraction ratios of 1.2 and 1.3 satisfied all critical low-speed inlet operating requirements for a fixed horizontal nacelle and tilt-nacelle-type subsonic V/STOL aircraft, respectively. Relative to a conventional axisymmetric tilt-nacelle inlet, the zero-length, slotted-lip inlet has a 27-percent smaller inlet lip contraction ratio, an 83-percent shorter total length, and a 5-percent smaller maximum cowl diameter.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-1245 , Joint Propulsion Conference; Jun 30, 1980 - Jul 02, 1980; Hartford, CT
    Format: text
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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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    Surface pressure measurements at two tips of a model helicopter rotor in hover (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Surface pressures were measured near the tip of a hovering single-bladed model helicopter rotor with two tip shapes. The rotor had a constant-chord, untwisted blade with a square, flat tip which could be modified to a body-of-revolution tip. Pressure measurements were made on the blade surface along the chordwise direction at six radial stations outboard of the 94 percent blade radius. Data for each blade tip configuration were taken at blade collective pitch angles of 0, 6.18 and 11.4 degrees at a Reynolds number of 736,000 and a Mach number of 0.25 both based on tip speed. Chordwise pressure distributions and constant surface pressure contours are presented and discussed.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3281
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Application of numerical optimization to the design of wings with specified pressure distributions (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A practical procedure for the optimum design of transonic wings is demonstrated. The procedure uses an optimization program based on the method of feasible directions coupled with an aerodynamic analysis program which solves the three-dimensional potential equation for subsonic through transonic flow. Two new wings for the A-7 aircraft were designed by using the optimization procedure to achieve specified surface pressure distributions. The new wings, along with the existing A-7 wing, were tested in the Ames 11 ft transonic wind tunnel. The experimental data show that all of the performance goals were met. However, comparisons of the wind tunnel results with the theoretical predictions indicate some differences at conditions for which strong shock waves occur.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3238
    Format: application/pdf
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  • 5
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    An alternating-direction-implicit algorithm for the unsteady potential equation in conservation form (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An implicit finite difference scheme for an efficient computation of unsteady potential flow about airfoils is presented. The formulation uses density and velocity potential as dependent variables, and is cast in conservation form to assure the theoretically correct determination of shockwave location and speed. To enable boundary conditions to be imposed directly on the airfoil surface, a time varying sheared rectilinear coordinate transformation is employed. Calculated time history solutions on a pulsating airfoil are compared with the results of another unsteady transonic code. It is concluded that the method has excellent numerical stability and gives accurate solutions with sharply resolved shocks.
    Keywords: AERODYNAMICS
    Type: NASA-CR-166152
    Format: application/pdf
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  • 6
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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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    NASA TECHNICAL REPORTS
  • 7
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    Study of cooling air inlet and exit geometries for horizontally opposed piston aircraft engines (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A semispan wing and nacelle of a typical general aviation twin-engine aircraft was tested to evaluate the cooling capability and drag of several nacelle shapes; the nacelle shapes included cooling air inlet and exit variations. The tests were conducted in the Ames Research Center's 40- by 80-Foot Wind Tunnel. It was found that the cooling air inlet geometry of opposed piston engine installations has a major effect on inlet pressure recovery, but only a minor effect on drag. Exit location showed a large effect on drag, especially for those locations on the sides of the nacelle where the suction characteristics were based on interaction with the wing surface pressures.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-1242 , Joint Propulsion Conference; Jun 30, 1980 - Jul 02, 1980; Hartford, CT
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Computation of three-dimensional viscous supersonic flow in inlets (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new approach has been developed for the computation of the three-dimensional viscous supersonic flow with embedded subsonic regions adjacent to solid boundaries and is applied to a mixed-compression supersonic inlet typical of current designs. The approach uses a reduced form of the three-dimensional Navier-Stokes equations so that the resultant equations can be treated as an initial boundary value problem and thus be solved by non-iterative forward marching in space. The numerical procedure utilizes an efficient consistently-split linearized block implicit technique to solve the finite difference analogues to the set of governing partial differential equations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-0194 , Aerospace Sciences Meeting; Jan 14, 1980 - Jan 16, 1980; Pasadena, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Transonic swept-wing analysis using asymptotic and other numerical methods (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper presents asymptotic methods for high-aspect-ratio wings in transonic flow developed for straight unyawed wings and for oblique wings. They show that the three-dimensional mixed-flow calculations may be reduced to solving a set of two-dimensional problems at each span station; the development of this theory and the related computational studies are reviewed. Differences between the piloted (oblique) wing, the swept-back wing, and the swept-forward-wing in the induced upwash are discussed; examples of similarity solutions are demonstrated for high subcritical and slightly supercritical component flows, and comparisons made with relaxation solutions of a full potential equation. The examples include oblique and symmetric swept wings, and the adequacy of the existing full-potential computer code is examined.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-0342 , Aerospace Sciences Meeting; Jan 14, 1980 - Jan 16, 1980; Pasadena, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Determination of an oblique wing aircraft's aerodynamic characteristics (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In this paper, the integration of wind tunnel and flight test procedures are studied for specifying aerodynamic model forms. A procedure is described which employs a stepwise regression method to systematically determine model structures and F-ratio statistics to rank the importance of each aerodynamic coefficient within a given model. Application of this technique and wind tunnel procedures to an oblique-wing aircraft indicate that the aircraft's measured and estimated response are in good agreement at both small and large wing skew angles
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 80-1630 , Atmospheric Flight Mechanics Conference; Aug 11, 1980 - Aug 13, 1980; Danvers, MA
    Format: text
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