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  • 1
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    PIAS: A program for an iterative aeroelastic solution (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A Program for an Iterative Aeroelastic Solution (PIAS) is discussed. This will be a modular computer program that combines the use of a finite-element structural analysis code with any linear or nonlinear aerodynamic code. At this point in time, PIAS has been designed but the software has not been written. The idea for this development originated with P. J. (Bud) Bobbitt of the NASA Langley Research Center. There was initial interest in an aeroelastic solution for a separation-induced leading-edge vortex. Some examples of the flow patterns for a low aspect ratio wing are shown. The Leading-Edge Vortex Program, which calculates pressure distributions including the effects of a separation-induced leading-edge vortex, uses an iterative solution method. This led to the concept of an iteration cycle on configuration shape external to the aerodynamic code.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 1; 15 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Comparisons of Theoretical and Experimental Pressure Distributions on an Arrow-Wing Configuration at Subsonic, Transonic, and Supersonic Speeds (1977)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A wind tunnel test of an arrow wing body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflection, has been conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions have been made using current state-of-the-art attached- and separated-flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for aeroelastic calculations and to explore the use of empirical methods to correct the theoretical methods where theory is deficient. It was determined that current state-of-the-art attached flow and empirical methods were inadequate to predict aeroelastic loads for this configuration.
    Keywords: AERODYNAMICS
    Type: AGARD Prediction of Aerodynamic Loading; 14 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Theoretical and experimental pressure distributions for a 71.2 degree swept arrow-wing configuration at subsonic, transonic, and supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A wind-tunnel test of an arrow-wing body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control-surface deflections, was conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using current state-of-the-art and newly developed attached- and separated-flow methods. Conditions were delineated under which these theories provide accurate basic and incremental aeroelastic loads predictions. Current state-of-the-art linear and nonlinear attached-flow methods were adequate only at small-angle-of-attack cruise conditions. Of the several separated-vortex methods evaluated, only the one utilizing a combination of linear source and quadratically varying doublet panels showed promise of yielding accurate loads distributions at moderate to large angles of attack.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Part 1; p 85-122
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    NASA TECHNICAL REPORTS
  • 4
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    A method for computing the leading-edge suction in a higher-order panel method (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental data show that the phenomenon of a separation induced leading edge vortex is influenced by the wing thickness and the shape of the leading edge. Both thickness and leading edge shape (rounded rather than point) delay the formation of a vortex. Existing computer programs used to predict the effect of a leading edge vortex do not include a procedure for determining whether or not a vortex actually exists. Studies under NASA Contract NAS1-15678 have shown that the vortex development can be predicted by using the relationship between the leading edge suction coefficient and the parabolic nose drag. The linear theory FLEXSTAB was used to calculate the leading edge suction coefficient. This report describes the development of a method for calculating leading edge suction using the capabilities of the higher order panel methods (exact boundary conditions). For a two dimensional case, numerical methods were developed using the double strength and downwash distribution along the chord. A Gaussian quadrature formula that directly incorporates the logarithmic singularity in the downwash distribution, at all panel edges, was found to be the best method.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3730 , NAS 1.26:3730 , D6-52135
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    NASA TECHNICAL REPORTS
  • 5
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    Specification for a Program for an Interative Aeroelastic Solution (PIAS) (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An engineering and software specification which was written for a computer program to calculate aeroelastic structural loads including the effects of nonlinear aerodynamics is presented. The procedure used in the program for an iterative aeroelastic solution (PIAS) is to alternately execute two computer codes: one to calculate aerodynamic loads for a specific wing shape, and another to calculate the deflected shape caused by this loading. A significant advantage to the design of PIAS is that the initial aerodynamic module can be replaced with others. The leading edge vortex (LEV) program is used as the aerodynamic module in PIAS. This provides the capability to calculate aeroelastic loads, including the effects of a separation induced leading edge vortex. The finite element method available in ATLAS Integrated structural analysis and design system is used to determine the deflected wing shape for the applied aerodynamics and inertia loads. The data management capabilities in ATLAS are used by the execution control monitor (ECM) of PIAS to control the solution process.
    Keywords: AERODYNAMICS
    Type: NASA-CR-172200 , NAS 1.26:172200 , D6-52134
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Transonic pressure measurements and comparison of theory to experiment for three arrow-wing configurations (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnel tests of arrow-wing body configurations consisting of flat, twisted, and cambered twisted wings, as well as a variety of leading and trailing edge control surface deflections, were conducted at Mach numbers from 0.4 to 1.05 to provide an experimental pressure data base for comparison with theoretical methods. Theory to experiment comparisons of detailed pressure distributions were made using state of the art attached flow methods. Conditions under which these theories are valid for these wings are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3434 , D6-51079-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Transonic pressure measurements and comparison of theory to experiment for an arrow-wing configuration. Volume 1: Experimental data report, base configuration and effects of wing twist and leading-edge configuration (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A wind tunnel test of an arrow-wing-body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflections, was conducted at Mach numbers from 0.4 to 1.1 to provide an experimental pressure data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using current state-of-the-art attached and separated flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for both flat and twisted wings and to explore the use of empirical methods to correct the theoretical methods where theory is deficient.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132727 , D6-42670-2-VOL-1
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    NASA TECHNICAL REPORTS
  • 8
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    Transonic pressure measurements and comparison of theory to experiment for an arrow-wing configuration. Volume 3: Data report, comparison of attached flow theories to experiment (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: For abstract, see N76-11034.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132729 , D6-42670-4-VOL-3
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    NASA TECHNICAL REPORTS
  • 9
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    Transonic pressure measurements and comparison of theory to experiment for an arrow-wing configuration. Volume 2: Experimental data report, effects of control surface deflection (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: For abstract, see N76-11034.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132728 , D6-42670-3-VOL-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    The prediction of pressure distributions on an arrow-wing configuration including the effect of camber, twist, and a wing fin (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wind tunnel tests of an arrow wing body configuration consisting of flat, twisted, and cambered twisted wings were conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. A variety of leading and trailing edge control surface deflections were included in these tests, and in addition, the cambered twisted wing was tested with an outboard vertical fin to determine its effect on wing and control surface loads. Theory experiment comparisons show that current state of the art linear and nonlinear attached flow methods were adequate at small angles of attack typical of cruise conditions. The incremental effects of outboard fin, wing twist, and wing camber are most accurately predicted by the advanced panel method PANAIR. Results of the advanced panel separated flow method, obtained with an early version of the program, show promise that accurate detailed pressure predictions may soon be possible for an aeroelasticity deformed wing at high angles of attack.
    Keywords: AERODYNAMICS
    Type: Supersonic Cruise Res. 1979, Pt. 1; p 59-115
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    NASA TECHNICAL REPORTS
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