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  • AERODYNAMICS  (671)
  • 2020-2024
  • 1985-1989  (671)
  • 1989  (671)
  • 1
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    High-alpha aerodynamic characteristics of crescent and elliptic wings (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: Static longitudinal and lateral-directional forces and moments were measured for elliptic- and crescent-wing models at high angles of attack in the NASA Langley 14-by-22-ft Subsonic Tunnel. The forces and moments were obtained for an angle-of-attack range including stall and post-stall conditions at a Reynolds number based on the average wing chord of about 1.8 million. Flow-visualization photographs using a mixture of oil and titanium-dioxide were also taken for several incidence angles. The force and moment data and the flow-visualization results indicated that the crescent wing model with its highly swept tips produced much better high-angle-of-attack aerodynamic characteristics than the elliptic model. Leading-edge separation-induced vortex flow over the highly swept tips of the crescent wing is thought to produce this improved behavior at high angles of attack. The unique planform design could result in safer and more efficient low-speed airplanes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-2240 , AIAA Applied Aerodynamics Conference; Jul 31, 1989 - Aug 02, 1989; Seattle, WA; United States
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    NASA TECHNICAL REPORTS
  • 2
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    NASA's CFD Validation Program (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: With computational fluid dynamics (CFD) becoming a productive research and design tool, the requirement to validate CFD codes has grown significantly. NASA had emphasized CFD validation activities since 1986 when a separate work element was formed to fund experimental activities related to validation. NASA's CFD and CFD validation programs are closely coordinated to ensure that experimental data bases are available as soon as possible for validating codes. In response to industry and academic requirements, four levels of experimental research have been defined as part of CFD validation with NASA's Aeronautics Advisory Committee (AAC) support although only the fourth level actually has the detailed information necessary for validating codes. Critical flow physics especially turbulence modeling are key to improved CFD codes. NASA has focused additional resources on transition and turbulence physics to meet these requirements. With improved turbulence models, CFD codes will be more accurate, robust, and efficient. However, with the level of detailed information available from CFD codes, highly accurate and detailed experiments are required to capture the critical information for validating codes. Advanced instrumentation especially non-intrusive instrumentation is required to acquire this information in validation experiments. The CFD validation program is being coordinated and managed to address these critical activities. A list of experiments which are currently being supported at least partially are included.
    Keywords: AERODYNAMICS
    Type: NASA, Ames Research Center, NASA Computational Fluid Dynamics Conference. Volume 1: Sessions 1-6; p 123-134
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    NASA TECHNICAL REPORTS
  • 3
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    Transonic Symposium: Theory, Application, and Experiment, volume 1, part 2 (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: In order to assess the state of the art in transonic flow disciplines and to glimpse at future directions, NASA-Langley held a Transonic Symposium. Emphasis was placed on steady, three dimensional external, transonic flow and its simulation, both numerically and experimentally. The symposium included technical sessions on wind tunnel and flight experiments; computational fluid dynamic applications; inviscid methods and grid generation; viscous methods and boundary layer stability; and wind tunnel techniques and wall interference. This, being volume 1, is unclassified.
    Keywords: AERODYNAMICS
    Type: NASA-CP-3020-VOL-1-PT-2 , L-16501-VOL-1-PT-2 , NAS 1.55:3020-VOL-1-PT-2 , Apr 19, 1988 - Apr 21, 1988; Hampton, VA; United States
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  • 4
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    Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 1 (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Topics addressed include: wind tunnel and flight experiments; computational fluid dynamics (CFD) applications, industry overviews; and inviscid methods and grid generations.
    Keywords: AERODYNAMICS
    Type: NASA-CP-3020-VOL-1-PT-1 , L-16501-VOL-1-PT-1 , NAS 1.55:3020-VOL-1-PT-1 , Apr 19, 1988 - Apr 21, 1988; Hampton, VA; United States
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  • 5
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    Numerical study of a delta planform with multiple jets in ground effect (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The flow past a 60-deg delta wing equipped with two thrust-reverser jets near the inboard trailing edge has been analyzed by numerical solution of the 3D thin-layer Navier-Stokes equations. An implicit, partially flux-split, approximately-factored Navier-Stokes solver coupled with a multiple grid embedding scheme has been adapted to this problem. Studies of the impact of numerical parameters (e.g., grid refinement and dissipation levels), and flow-field parameters such as the height of the delta wing above the ground plane and the jet size on the solution, were performed. Results of these numerical studies indicate some challenges in the accurate resolution of complex 3D free shear layers and jets. Nevertheless, flow features such as jet deformation and ground vortex formation observed in experimental flow visualizations are captured. Further, comparisons with experimental data confirm the ability to simulate the loss of wing-borne lift, commonly referred to 'suckdown, as the delta planform flies at slow speeds in close proximity to the ground. Detailed analysis of the numerical results has also given additional insight into the structure of the ground vortex and the mechanisms of lift loss.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 892283 , ; 15 p.|SAE, Aerospace Technology Conference and Exposition; Sept. 25-28, 1989; Anaheim, CA; United States
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  • 6
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    Prediction of transitional (laminar-turbulent) hypersonic flows using the parabolized Navier-Stokes equations (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Hypersonic transitional flow predictions have been made using the parabolized Navier-Stokes equations with an algebraic transition/turbulence model by appropriately modulating the turbulent viscosity with the available intermittency functions for incompressible and compressible flows. A comparison between the predictions with and without a low Reynolds number correction has also been made. The predictions are compared with the available experimental data and with the theory over a range of Mach number. A simple Re(theta)/M(delta) criterion is shown to satisfactorily predict the meridional variation of the onset location of transition on a cone at a small angle of attack, whereas none of the correlations discussed can do that. Various available correlations are discussed vis-a-vis the predictions as to the locations of the onset and the end of transition.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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  • 7
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    On hypersonic shock layer and its extension beyond the Navier-Stokes level (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: An extension of the continuum model beyond the Navier-Stokes (NS) level and related issues on problem formulation are examined for a hypersonic shock layer on the basis of Grad's thirteen-moment equations for a Maxwell gas. The 13-moment system, simplified consistently with a fully viscous version of the thin shock-layer approximation, permits correlation with the corresponding NS-based solution. With the exception of pressure and density, several flow properties including normal stress, shear stress and normal heat flux along a streamline are unaffected by translational nonequilibrium and are therefore predicted correctly by the NS solution to the leading order, even in a domain far from translational equilibrium where molecular-transport processes rank equally with the convection.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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  • 8
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    2-D and 3-D mixing flow analyses of a scramjet-afterbody configuration (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A cold simulant gas study of propulsion/airframe integration for a hypersonic vehicle powered by a scramjet engine is presented. The specific heat ratio of the hot exhaust gases are matched by utilizing a cold mixture of argon and Freon-12. Solutions are obtained for a hypersonic corner flow and a supersonic rectangular flow in order to provide the upstream boundary conditions. The computational test examples also provide a comparison of this flow with that of air as the expanding supersonic jet, where the specific heats are assumed to be constant. It is shown that the three-dimensional computational fluid capabilities developed for these types of flow may be utilized to augment the conventional wind tunnel studies of scramjet afterbody flows using cold simulant exhaust gases, which in turn can help in the design of a scramjet internal-external nozzle.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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    NASA TECHNICAL REPORTS
  • 9
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    Hypersonic rarefied-flow aerodynamics inferred from Shuttle Orbiter acceleration measurements (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Data obtained from multiple flights of sensitive accelerometers on the Space Shuttle Orbiter during reentry have been used to develop an improved aerodynamic model for the Orbiter normal- and axial-force coefficients in hypersonic rarefied flow. The lack of simultaneous atmospheric density measurements was overcome in part by using the ratio of normal-to-axial acceleration, in which density cancels, as a constraint. Differences between the preflight model and the flight-acceleration-derived model in the continuum regime are attributed primarily to real gas effects. New insights are gained into the variation of the force coefficients in the transition between the continuum regime and free molecule flow.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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  • 10
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    Review of a code development and calibration program in support of the aeroassist flight experiment (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The code development and calibration program for the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) is reviewed, with emphasis directed toward support of the Aeroassist Flight Experiment (AFE). The flight project is designed to obtain data which will be used in the validation of computational fluid dynamic approximation methods. Comparisons between experimental data and numerical simulation focus on perfect-gas tests over a scale model of the AFE and on flight and ground tests which challenge some aspect of the thermochemical nonequilibrium model. In the first case, the gas model is simple, but the grid-related problems of defining the real vehicle are present. In the second case, the vehicle geometries are simple, but thermochemical processes must be modeled correctly in order to compare with the experimental data. These comparisons are described as calibration runs because they test elements of the numerical simulation, but no single data set adequately simulates the full-scale AFE flight conditions. Comparisons between computation and experiment over a broad range of data sets show generally good agreement, though some aspects of the numerical model require further development.
    Keywords: AERODYNAMICS
    Type: International Conference on Hypersonic Aerodynamics; Sept. 4-6, 1989; Manchester
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