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  • 1
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    Evaluation of 3-D graphics software: A case study (1984)
    In:  CASI
    Details
    Publication Date: 2006-04-09
    Description: An efficient 3-D geometry graphics software package which is suitable for advanced design studies was developed. The advanced design system is called GRADE--Graphics for Advanced Design. Efficiency and ease of use are gained by sacrificing flexibility in surface representation. The immediate options were either to continue development of GRADE or to acquire a commercially available system which would replace or complement GRADE. Test cases which would reveal the ability of each system to satisfy the requirements were developed. A scoring method which adequately captured the relative capabilities of the three systems was presented. While more complex multi-attribute decision methods could be used, the selected method provides all the needed information without being so complex that it is difficult to understand. If the value factors are modestly perturbed, system Z is a clear winner based on its overall capabilities. System Z is superior in two vital areas: surfacing and ease of interface with application programs.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Langley Research Center Computer-Aided Geometry Modeling; p 359-376
    Format: text
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  • 2
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    Projected role of advanced computational aerodynamic methods at the Lockheed-Georgia company (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Experience with advanced computational methods being used at the Lockheed-Georgia Company to aid in the evaluation and design of new and modified aircraft indicates that large and specialized computers will be needed to make advanced three-dimensional viscous aerodynamic computations practical. The Numerical Aerodynamic Simulation Facility should be used to provide a tool for designing better aerospace vehicles while at the same time reducing development costs by performing computations using Navier-Stokes equations solution algorithms and permitting less sophisticated but nevertheless complex calculations to be made efficiently. Configuration definition procedures and data output formats can probably best be defined in cooperation with industry, therefore, the computer should handle many remote terminals efficiently. The capability of transferring data to and from other computers needs to be provided. Because of the significant amount of input and output associated with 3-D viscous flow calculations and because of the exceedingly fast computation speed envisioned for the computer, special attention should be paid to providing rapid, diversified, and efficient input and output.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Ames Res. Center Future Computer Requirements for Computational Aerodynamics; p 108-120
    Format: text
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  • 3
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    The prediction of nonlinear longitudinal combustion instability in liquid propellant rockets (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analytical technique was developed to solve nonlinear longitudinal combustion instability problems. The analysis yields the transient and limit cycle behavior of unstable motors and the threshold amplitude required to trigger a linearly stable motor into unstable operation. The limit cycle waveforms were found to exhibit shock wave characteristics for most unstable engine operating conditions. A method of correlating the analytical solutions with experimental data was developed. Calculated results indicate that a second-order solution adequately describes the behavior of combustion instability oscillations over a broad range of engine operating conditions, but that higher order effects must be accounted for in order to investigate engine triggering.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-120904
    Format: application/pdf
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  • 4
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    Analysis of a theoretically optimized transonic airfoil (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Numerical optimization was used in conjunction with an inviscid, full potential equation, transonic flow analysis computer code to design an upper surface contour for a conventional airfoil to improve its supercritical performance. The modified airfoil was tested in a compressible flow wind tunnel. The modified airfoil's performance was evaluated by comparison with test data for the baseline airfoil and for an airfoil developed by optimization of leading edge of the baseline airfoil. While the leading edge modification performed as expected, the upper surface re-design did not produce all of the expected performance improvements. Theoretical solutions computed using a full potential, transonic airfoil code corrected for viscosity were compared to experimental data for the baseline airfoil and the upper surface modification. These correlations showed that the theory predicted the aerodynamics of the baseline airfoil fairly well, but failed to accurately compute drag characteristics for the upper surface modification.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3065 , LG78ER0212
    Format: application/pdf
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  • 5
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    Summary of combustion instability research, 1 August 1969 - 31 July 1970 (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Predicting nonlinear behavior of unstable liquid propellant rocket motors by Galerkin method
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-113602 , REPT-70-5
    Format: application/pdf
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  • 6
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    Numerical optimization - An assessment of its role in transport aircraft aerodynamic design through a case study (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An efficient transonic wing design procedure based upon numerical optimization together with three-dimensional transonic methods has been developed and used to design an advanced transport wing. The method development included an examination of the use of both full potential and extended small disturbance analysis codes and demonstrated that the former formulation was more reliable. In either case, the design procedure is economical and easy to use. Design verification in a unique semi-span test arrangement demonstrated that the design method produced a wing which satisfied the study design requirements. However, aeroelastic deformation of the wing occurred during the wind tunnel test. The computational methods used in the design procedure were employed to assess the effect of the aeroelastic deformation. The paper concludes with an evaluation of the design procedure and recommendation for its improvement.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: International Council of the Aeronautical Sciences, Congress; Oct 12, 1980 - Oct 17, 1980; Munich; Germany
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  • 7
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    Nonlinear longitudinal combustion instability in rocket motors. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new analytical technique for the solution of nonlinear longitudinal combustion instability problems in rocket combustors is developed. Using relatively little computation time, this technique is capable of predicting the transient and limit cycle behavior of the combustion instability oscillations as well as the disturbance amplitude required to trigger an instability in a linearly stable motor. The limit cycle waveforms are found to exhibit shock wave characteristics for most unstable engine operating conditions. It is shown that the characteristics of the resulting instability are independent of the nature of the initial disturbance and they depend solely upon the engine operating conditions and the characteristics of the unsteady combustion process.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA PAPER 73-217 , Aerospace Sciences Meeting; Jan 10, 1973 - Jan 12, 1973; Washington, DC
    Format: text
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  • 8
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    Application of the Galerkin Method in the Design of Stable Liquid Rocket Motors (1972)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A brief description of results obtained in the continuing investigations is presented. The following areas are covered: (1) the development of the third-order, multimode theory to study the behavior of large amplitude transverse instabilities, (2) nonlinear axial mode instability, and (3) the influence of the functional form of the unsteady combustion response function upon the stability characteristics of rocket motors. Also a study was begun to improve the second order potential theory in order to provide a better approximation to the nozzle boundary condition.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-125818 , SAR-7
    Format: application/pdf
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  • 9
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    Supercritical wing design using numerical optimization and comparisons with experiment (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A numerical minimization scheme is used in conjunction with two-dimensional and three-dimensional inviscid transonic flow analysis codes to provide procedures for wing leading edge aerodynamic design. The procedures are demonstrated in the design of a new leading edge to improve C-141 cruise performance. For the high aspect ratio moderately swept C-141 wing, the 2-D procedure is shown to yield results which are in close agreement with those obtained using the 3-D technique. Although the 2-D approach uses much less computation time than the 3-D technique, the latter requires fewer manhours than the former. Comparisons of predicted and wind tunnel measured performance improvements are presented which verify the design procedures.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 79-0065 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 15, 1979 - Jan 17, 1979; New Orleans, LA
    Format: text
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