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  • 1
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 26; 650-656
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  • 2
    Publication Date: 2019-07-13
    Description: The NASA X-43 "Hyper-X" hypersonic research vehicle will be boosted to a Mach 7 flight test condition mounted on the nose of an Orbital Sciences Pegasus launch vehicle. The separation of the research vehicle from the Pegasus presents some unique aerodynamic problems, for which computational fluid dynamics has played a role in the analysis. This paper describes the use of several CFD methods for investigating the aerodynamics of the research and launch vehicles in close proximity. Specifically addressed are unsteady effects, aerodynamic database extrapolation, and differences between wind tunnel and flight environments.
    Keywords: Aerodynamics
    Type: AIAA Paper 2000-4009 , Applied Aerodynamics; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
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  • 3
    Publication Date: 2019-07-13
    Description: Computational fluid dynamics (CFD) tools have been used extensively in the analysis and development of the X-43A Hyper-X Research Vehicle (HXRV). A significant element of this analysis is the prediction of integrated vehicle aero-propulsive performance, which includes an integration of aerodynamic and propulsion flow fields. This paper describes analysis tools used and the methodology for obtaining pre-flight predictions of longitudinal performance increments. The use of higher-fidelity methods to examine flow-field characteristics and scramjet flowpath component performance is also discussed. Limited comparisons with available ground test data are shown to illustrate the approach used to calibrate methods and assess solution accuracy. Inviscid calculations to evaluate lateral-directional stability characteristics are discussed. The methodology behind 3D tip-to-tail calculations is described and the impact of 3D exhaust plume expansion in the afterbody region is illustrated. Finally, future technology development needs in the area of hypersonic propulsion-airframe integration analysis are discussed.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2000-4010 , Applied Aerodynamics; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
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  • 4
    Publication Date: 2019-07-10
    Description: Results from a study to assess the accuracy of turbulent heating and skin friction prediction techniques for hypersonic applications are presented. The study uses the original and a modified Baldwin-Lomax turbulence model with a space marching code. Grid converged turbulent predictions using the wall damping formulation (original model) and local damping formulation (modified model) are compared with experimental data for several flat plates. The wall damping and local damping results are similar for hot wall conditions, but differ significantly for cold walls, i.e., T(sub w) / T(sub t) 〈 0.3, with the wall damping heating and skin friction 10-30% above the local damping results. Furthermore, the local damping predictions have reasonable or good agreement with the experimental heating data for all cases. The impact of the two formulations on the van Driest damping function and the turbulent eddy viscosity distribution for a cold wall case indicate the importance of including temperature gradient effects. Grid requirements for accurate turbulent heating predictions are also studied. These results indicate that a cell Reynolds number of 1 is required for grid converged heating predictions, but coarser grids with a y(sup +) less than 2 are adequate for design of hypersonic vehicles. Based on the results of this study, it is recommended that the local damping formulation be used with the Baldwin-Lomax and Cebeci-Smith turbulence models in design and analysis of Hyper-X and future hypersonic vehicles.
    Keywords: Aerodynamics
    Type: NASA/CR-2001-210837 , NAS 1.26:210837
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  • 5
    Publication Date: 2019-07-13
    Description: An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: AIAA Paper 99-4911 , Weakly Ionized Gases; Nov 01, 1999 - Nov 05, 1999; Norfolk, VA; United States|International Space Planes and Hypersonic Systems and Technoogies; Nov 01, 1999 - Nov 05, 1999; Norfolk, VA; United States
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  • 6
    Publication Date: 2019-07-13
    Description: The wind tunnel and flight data from the X-15 program have been evaluated for utilization in CFD calibration research. From the analysis, experimental data suitable for CFD code calibration are identified.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-5047 , ; 12 p.|AIAA, International Aerospace Planes Conference; Dec 01, 1992 - Dec 04, 1992; Orlando, FL; United States
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  • 7
    Publication Date: 2019-07-13
    Description: Perfect gas computational results from a newly-developed upwind, parabolized Navier-Stokes (PNS) solver are compared with an existing set of experimental laminar results for a 10-deg half-angle circular cone at freestream Mach number of 7.95. Comparisons were performed with surface pressure and heat transfer data, as well as with flowfield pitot measurements. The PNS code predicted the surface quantities accurately up through 20-deg angle-of-attack, including crossflow separation, and correctly defined the location of the bow shock and the edge of the boundary layer. The importance of cell Reynolds number, grid density, and thermal boundary conditions to the accurate prediction of the flowfield are examined through numerical emamples.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-2566 , AIAA Applied Aerodynamics Conference; Jun 06, 1988 - Jun 08, 1988; Williamsburg, VA; United States
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  • 8
    Publication Date: 2019-07-13
    Description: Computational analyses have been performed for the initial assessment of flight research vehicle concepts that satisfy requirements for potential hypersonic experiments. Results were obtained from independent analyses at NASA Ames, NASA Langley, and Sandia National Labs, using sophisticated time-dependent Navier-Stokes and parabolized Navier-Stokes methods. Careful study of a common problem consisting of hypersonic flow past a slightly blunted conical forebody was undertaken to estimate the level of uncertainty in the computed results, and to assess the capabilities of current computational methods for predicting boundary-layer transition onset. Results of this study in terms of surface pressure and heat transfer comparisons, as well as comparisons of boundary-layer edge quantities and flow-field profiles are presented here. Sensitivities to grid and gas model are discussed. Finally, representative results are presented relating to the use of Computational Fluid Dynamics in the vehicle design and the integration/support of potential experiments.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-0312 , ; 12 p.|AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States
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  • 9
    Publication Date: 2019-07-10
    Description: An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/TM-1999-209828 , L-17915 , NAS 1.15:209828
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  • 10
    Publication Date: 2019-07-13
    Description: A pre-flight analysis was conducted for the Mach 7 and Mach 10 X-43 cowl-closed configurations to evaluate three-dimensional flow-field effects on localized heating in the vicinity of the closed cowl flap and sidewall. First, engineering-level analyses based on documented laminar and turbulent surface heating database were used to estimate localized heating amplification factors to account for turbulent flow effects, corner flow effects and the presence of forebody boundary layer trip devices. These estimated factors were applied to 2-D computational predictions to develop surface heat loads. Second, thin-film gauge surface heating data were obtained for a Mach 10 cowl-closed configuration in a reflected shock tunnel at simulated flight conditions. Third, computational fluid dynamics (CFD) flow-field predictions were obtained at Mach 10 ground test conditions to provide comparisons with the engineering database predictions and experimental measurements. Similarly, a CFD solution was also obtained at Mach 7 flight conditions to provide qualitative comparisons with engineering predictions. The Mach 10 CFD predictions compare favorably with the experimental measurements and the engineering estimates for surface heating amplification on the closed cowl. However, experimental measurements were not of sufficient quantity on the sidewall surface to capture the highest localized heating rates, and also the Mach 10 CFD predictions suggest higher peak heating on the sidewall compared to the engineering estimates. Also, the Mach 7 CFD predictions indicate qualitative agreement with the database estimates in terms of flow-field structure and peak heating locations on the closed-cowl flap and sidewall surfaces.
    Keywords: Aircraft Design, Testing and Performance
    Type: AIAA Paper 2002-0218 , 40th AIAA Aerospace Sciences Conference and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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