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  • 11
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    ALESEP: A computer program for the analysis of airfoil leading edge separation bubbles (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The ALESEP program for the analysis of the inviscid/viscous interaction which occurs due to the presence of a closed laminar transitional separation bubble on an airflow is presented. The ALESEP code provides a iterative solution of the boundary layer equations expressed in an inverse formulation coupled to a Cauchy integral representation of the inviscid flow. This interaction analysis is treated as a local perturbation to a known solution obtained from a global airfoil analysis. Part of the required input to the ALESEP code are the reference displacement thickness and tangential velocity distributions. Special windward differencing may be used in the reversed flow regions of the separation bubble to accurately account for the flow direction in the discretization of the streamwise convection of momentum. The ALESEP code contains a forced transition model based on a streamwise intermittency function and a natural transition model based on a solution of the integral form of the turbulent kinetic energy equation. Instructions for the input/output, and program usage are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-172310 , NAS 1.26:172310
    Format: application/pdf
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  • 12
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    Navier-Stokes computations of prolate spheroids at angle of attack (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Three-dimensional viscous flow calculations are made for a 6:1 prolate spheroid at conditions for which detailed experimental data are available. The computations are made with two finite-volume algorithms for the compressible Navier-Stokes equations, one using central differencing for the convective and pressure terms and the other using an upwind-biased flux-difference-splitting approach. The effects of grid density and artificial dissipation on the accuracy of the numerical results are included. Generally good agreement of the computations with the experimental results is obtained over a range of Reynolds numbers and angles-of-attack, up to 30 deg, although the results at lower Reynolds numbers are sensitive to the assumed transition location.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-2627
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  • 13
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    Viscid/inviscid interaction analysis of separated trailing-edge flows (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 481-489
    Format: text
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  • 14
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    Analysis of airfoil leading-edge separation bubbles (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A local inviscid-viscous interaction technique was developed for the analysis of low speed airfoil leading edge transitional separation bubbles. In this analysis an inverse boundary layer finite difference analysis is solved iteratively with a Cauchy integral representation of the inviscid flow which is assumed to be a linear perturbation to a known global viscous airfoil analysis. Favorable comparisons with data indicate the overall validity of the present localized interaction approach. In addition numerical tests were performed to test the sensitivity of the computed results to the mesh size, limits on the Cauchy integral, and the location of the transition region.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 83-0300 , AIAA Journal (ISSN 0001-1452); 22; 1697-170
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  • 15
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    The use of Levy-Lees variables in three-dimensional boundary-layer flows (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A method for solving a general class of three-dimensional boundary layer flows is developed. In the development, Levy-Lees variables are extended to three dimensions and equations are placed in these similarity variables. An implicit finite difference scheme which is stable for negative transverse velocities is used to solve these equations. The method developed is applied to obtain solutions for sharp and spherically blunted circular cones at angle of attack. Longitudinal and transverse distributions are presented for these cases. Good agreement is found with the results obtained by other numerical schemes and the experimental data of Tracy, for sharp circular cones at angle of attack. For spherically blunted cones at angle of attack, the results are in good agreement with axisymmetric sphere results up to the region where spherical symmetry holds.
    Keywords: FLUID MECHANICS
    Type: NASA-CR-112315
    Format: application/pdf
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  • 16
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    Transonic Navier-Stokes flow computations over wing-fuselage geometries (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The steady-state transonic viscous flows over two wing-fuselage configurations are solved numerically. The 3D compressible thin-layer Navier-Stokes equations are solved by means of multistage timestepping similar to the Runge-Kutta method. The timestepping technique is applied with a multigrid scheme to make the transonic Navier-Stokes computations using the Baldwin-Lomax turbulence for closure and converging the solution on a grid of 1.52 million grid points with a C-O topology. Both generic and fighter wing-fuselage geometries are solved, and the results are compared to experimental studies. Solution convergence is found to be fast, and the fine grid generates accurate results for both configurations by means of the Baldwin-Lomax turbulence model. Results from the Johnson-King model calculations produce results that are more consistent with experimental results for the fighter configuration.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-3205 , AIAA Applied Aerodynamics Conference; Sept. 23-25, 1991; Baltimore, MD; United States
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  • 17
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    Navier-Stokes calculations for DFVLR F5-wing in wind tunnel using Runge-Kutta time-stepping scheme (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A three-dimensional Navier-Stokes code using an explicit multistage Runge-Kutta type of time-stepping scheme is used for solving the transonic flow past a finite wing mounted inside a wind tunnel. Flow past the same wing in free air was also computed to assess the effect of wind-tunnel walls on such flows. Numerical efficiency is enhanced through vectorization of the computer code. A Cyber 205 computer with 32 million words of internal memory was used for these computations.
    Keywords: AERODYNAMICS
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  • 18
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    Quasi-three-dimensional laminar boundary-layer separations in supersonic flow (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A numerical algorithm is presented for solving laminar, steady, supersonic interacting boundary-layer flows for quasi-three-dimensional configurations. The interaction problem is treated as a boundary-value problem and a salient feature of the scheme is the direct implementation of the downstream boundary condition. Solutions are presented for axisymmetric and swept (yawed) compression ramps for both adiabatic and heat transfer conditions over a Mach number range of 2-6. The results are in good agreement with experimental data and existing theories for axisymmetric cases. For the swept (yawed) configurations, lack of experimental data makes a direct comparison impossible, but the present solutions are found to be in qualitative agreement with earlier studies. In addition it is shown that the trends obtained here for the sweep effects are well predicted by a simple extension of the two-dimensional asymptotic theory.
    Keywords: AERODYNAMICS
    Type: Winter Annual Meeting on Numerical/laboratory computer methods in fluid mechanics; Dec 05, 1976 - Dec 10, 1976; New York, NY
    Format: text
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  • 19
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    Analysis of airfoil leading edge separation bubbles (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: (Previously announced in STAR as N83-10018)
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 83-0300 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 10, 1983 - Jan 13, 1983; Reno, NV
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  • 20
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    Comparison of solutions of the Navier-Stokes and interacting boundary layer equations for separated turbulent flow (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Comparisons are presented between numerical solutions of the Navier-Stokes and interacting boundary-layer equations for the subsonic separated turbulent flow over an axisymmetric boattail configuration for which experimental data was available. Comparisons were made using a standard algebraic turbulence model and its modification using a streamwise relaxation model. Grid size studies were performed to provide an approximate assessment of the sensitivity of each method to mesh size. In general, good agreement was observed between the solutions of the Navier-Stokes and interacting boundary-layer equations; however, the interaction approach responded more strongly to the modified turbulence model thereby giving better agreement with experimental data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Format: text
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