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  • 1
    Publication Date: 1996-07-01
    Print ISSN: 0048-6604
    Electronic ISSN: 1944-799X
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2013-08-31
    Description: A unified formulation is presented based on the full potential framework coupled with an appropriate structural model to compute steady and unsteady flows over rigid and flexible configurations across the Mach number range. The unsteady form of the full potential equation in conservation form is solved using an implicit scheme maintaining time accuracy through internal Newton iterations. A flux biasing procedure based on the unsteady sonic reference conditions is implemented to compute hyperbolic regions with moving sonic and shock surfaces. The wake behind a trailing edge is modeled using a mathematical cut across which the pressure is satisfied to be continuous by solving an appropriate vorticity convection equation. An aeroelastic model based on the generalized modal deflection approach interacts with the nonlinear aerodynamics and includes both static as well as dynamic structural analyses capability. Results are presented for rigid and flexible configurations at different Mach numbers ranging from subsonic to supersonic conditions. The dynamic response of a flexible wing below and above its flutter point is demonstrated.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Unsteady Aerodynamics and Aeroelasticity 1987, Part 1; p 175-191
    Format: application/pdf
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  • 3
    Publication Date: 2013-08-31
    Description: A framework is presented for developing computationally unified numerical algorithms for solving nonlinear equations that arise in modeling various problems in mathematical physics. The concept of computational unification is an attempt to encompass efficient solution procedures for computing various nonlinear phenomena that may occur in a given problem. For example, in Computational Fluid Dynamics (CFD), a unified algorithm will be one that allows for solutions to subsonic (elliptic), transonic (mixed elliptic-hyperbolic), and supersonic (hyperbolic) flows for both steady and unsteady problems. The objectives are: development of superior unified algorithms emphasizing accuracy and efficiency aspects; development of codes based on selected algorithms leading to validation; application of mature codes to realistic problems; and extension/application of CFD-based algorithms to problems in other areas of mathematical physics. The ultimate objective is to achieve integration of multidisciplinary technologies to enhance synergism in the design process through computational simulation. Specific unified algorithms for a hierarchy of gas dynamics equations and their applications to two other areas: electromagnetic scattering, and laser-materials interaction accounting for melting.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Ames Research Center, Supercomputing in Aerospace; p 87-107
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: The steady form of the full potential equation, in conservative form, is employed to analyze and design a wide variety of complex aerodynamic shapes. The nonlinear method is based on the theory of characteristic signal propagation coupled with novel flux biasing concepts and body-fitted mapping procedures. The resulting codes are vectorized for the CRAY XMP and the VPS-32 supercomputers. Use of the full potential nonlinear theory is demonstrated for a single-point supersonic wing design and a multipoint design for transonic maneuver/supersonic cruise/maneuver conditions. Achievement of high aerodynamic efficiency through numerical design is verified by wind tunnel tests. Other studies reported include analyses of a canard/wing/nacelle fighter geometry.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3982 , NAS 1.26:3982
    Format: application/pdf
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  • 5
    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 495-53
    Format: text
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  • 6
    Publication Date: 2019-06-28
    Description: For fully supersonic flows, an efficient strategy for obtaining numerical solutions is to employ space marching techniques. A full potential marching technique, known as the SIMP code and capable of handling such embedded subsonic regions, has achieved some success analyzing low supersonic Mach number flows. The extension of the full potential approach to the Euler equation which model the exact nonlinear inviscid gas dynamic flow processes is presented. Within the assumption of an inviscid flow, such an Euler marching solver can be applied to a wide class of shocked flows including the hypersonic range. The intent is to maintain some of the basic features of the full potential SIMP code within the Euler solver in dealing with geometry input, gridding techniques, and input/output routines including post processing of results. An Euler marching code known as EMTAC was developed. Results obtained for a variety of configurations involving canard, wing, horizontal tail, flow-through inlet, and fuselage using both the EMTAC and SIMP codes are reported. For shocked cases satisfying the isentropic assumption, the EMTAC and SIMP codes produced practically the same results. In terms of execution time, the EMTAC code is slower.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4085 , NAS 1.26:4085
    Format: application/pdf
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  • 7
    Publication Date: 2019-07-12
    Description: EMTAC (Euler Marching Technique For Accurate Computation) computer program employs Euler marching algorithm for computing supersonic flows. Enables accurate nonlinear analysis of nonlinear dynamics of supersonic flow over wide range of supersonic mach numbers and angles of attack. Based on exact equations of dynamics of inviscid gas and valid for computations of flows at low and high supersonic mach numbers exhibiting strong shocks and rotational effects. Program also used for inviscid three-dimensional flows fully subsonic or transonic (subsonic with supersonic pockets). Written in FORTRAN V.
    Keywords: MECHANICS
    Type: LAR-14228 , NASA Tech Briefs (ISSN 0145-319X); 16; 1; P. 56
    Format: text
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  • 8
    Publication Date: 2019-07-12
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 25; 230-238
    Format: text
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  • 9
    Publication Date: 2019-07-13
    Description: A finite-volume discretization procedure derived from proven CFD methods is used to solve the conservation form of the time-domain Maxwell's equations, in order to compute EM scattering from layered objects. This time-domain approach handles both single-frequency/continuous wave and broadband-frequency/pulse incident excitation. Arbitrarily shaped objects are modeled by means of a body-fitted coordinate transformation; complex internal/external structures with many material layers are treated through the implementation of a multizone framework capable of handling any type of zonal boundary condition. Results are presented for various two- and three-dimensional problems.
    Keywords: PHYSICS (GENERAL)
    Type: AIAA PAPER 90-3055 , AIAA Applied Aerodynamics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
    Format: text
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