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  • 1
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    Numerical study of shock-wave/boundary-layer interactions with bleed (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A numerical study was conducted to investigate how bleed through a two-dimensional slot affects shock-wave induced, boundary-layer separation on a flat plate. This study is based on the ensemble-averaged, compressible, Navier-Stokes equations closed by the Baldwin-Lomax, algebraic turbulence model. The algorithm used to obtain solutions was the implicit, partially split, two-factored scheme of Steger. This study examined the effects of the following parameters in controlling shock-wave induced flow separation: location of slot in relation to where the incident shock wave impinged on the boundary layer, size of slot in relation to the boundary-layer thickness, number of slots, spacings between slots, and strength of the incident shock wave. This study also showed the nature of the very complex flowfield about the slot or slots and how the plenum affects the bleed process. The results of this study are relevant to problems where bleed is used to control shock-wave induced, boundary-layer separation (e.g., inside jet engine inlets and wind tunnels).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 31; 5; p. 869-876.
    Format: text
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  • 2
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    Implicit treatment of diffusion terms in lower-upper algorithms (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A method is presented which allows diffusion terms to be treated implicitly in the lower-upper (LU) algorithm (which is a commonly used method for solving 'compressible' Euler and Navier-Stokes equations) so that the algorithm's good stability properties will not be impaired. The new method generalizes the concept of LU factorization from that associated with the sign of eigenvalues to that associated with backward- and forward-difference operators without regard to eigenvalues. The method is verified in a turbulent boundary layer study.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 31; 4; p. 788-791.
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  • 3
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    Navier-Stokes simulation of flow through a highly contoured subsonic diffuser (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The flow through a highly offset subsonic diffuser with cross-sectional profiles that varied from rectangular at the duct entrance to circular at the engine face was numerically simulated. A multizonal approach combined with a two-grid topology was used to represent both the internal and external flowfields, and an implicit, approximately-factored, partially flux-split finite-difference algorithm was used to solve the three-dimensional thin-layer Navier-Stokes equations. The computed static pressures along the inlet wall and total pressures on the engine face were compared with experimental data. In addition, the overall flowfield within the duct was examined in detail. Good agreement is shown between experiment and computations, with the limiting factor being the lack of a reliable turbulence model for internal flow problems.
    Keywords: AERODYNAMICS
    Type: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 34; 473-483
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  • 4
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    Bleed-boundary conditions for numerically simulated mixed-compression supersonic inlet flow (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A numerical study was performed to investigate boundary conditions for bleed openings that are needed in the numerical simulation of critical flow through turbojet inlets with bleed. Nine different boundary conditions (BCs) were devised and examined. Of the BCs examined, three were able to stabilize the terminal shock near the inlet's throat. This numerical study was based on the ensemble-averaged, unsteady, three-dimensional, compressible Navier-Stokes equations closed by the Baldwin-Lomax algebraic turbulence model. Solutions to the Navier-Stokes equations were obtained by using a hybrid implicit-explicit method (Beam and Warming/MacCormack). The multiblock grid system used in the solution procedure was generated by solving a set of elliptic partial differential equations. Solutions obtained were compared with available experimental data.
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 8; 4, Ju
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  • 5
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    Approximate factorization with source terms (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A comparative evaluation is made of three methodologies with a view to that which offers the best approximate factorization error. While two of these methods are found to lead to more efficient algorithms in cases where factors which do not contain source terms can be diagonalized, the third method used generates the lowest approximate factorization error. This method may be preferred when the norms of source terms are large, and transient solutions are of interest.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA Journal (ISSN 0001-1452); 29; 1759
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  • 6
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    Calculation of external-internal flow fields for mixed-compression inlets (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Supersonic inlet flows with mixed external-internal compressions were computed using a combined implicit-explicit (Beam-Warming-Steger/MacCormack) method for solving the three-dimensional unsteady, compressible Navier-Stokes equations in conservation form. Numerical calculations were made of various flows related to such inlet operations as the shock-wave intersections, subsonic spillage around the cowl lip, and inlet started versus unstarted conditions. Some of the computed results were compared with wind tunnel data.
    Keywords: AERODYNAMICS
    Type: Computer Methods in Applied Mechanics and Engineering (ISSN 0045-7825); 64; 21-37
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  • 7
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    Pressure-fluctuation inputs and response of panels underlying attached and separated supersonic turbulent boundary layers (1973)
    In:  CASI
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    Publication Date: 2012-05-23
    Description: Results of an investigation of surface pressure fluctuations and response of panels underlying attached and separated turbulent boundary layers and shock waves are summarized. Extensive tests of a large assortment of axisymmetric and two-dimensional models have been conducted at transonic and supersonic Mach numbers to 3.6 to study the pressure fields. Assorted fixed-edge flat panels have been tested at Mach numbers from 1.6 to 3.6 in attached and completely separated flow fields and also in mixed flow with a step induced shock wave oscillating on the panels. The surface pressure fluctuations are described in terms of broadband rms, spectral density, and spatial correlation information. The effectiveness of parameters for scaling the pressure fluctuations is also illustrated. Measurements of the amplitude and strain response of the panels are compared with response computations by the normal method of analysis.
    Keywords: FLUID MECHANICS
    Type: AGARD Symp. on Acoustic Fatigue; 20 p
    Format: text
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  • 8
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    Navier-Stokes solutions for mixed compression axisymmetric inlet flow with terminal shock (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 5; 4
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  • 9
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    Numerical studies of unsteady transonic flow over oscillating airfoil (1985)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A finite difference solution to the Navier-Stokes equations combined with a time varying grid generation technique was used to compute unsteady transonic flow over an oscillating airfoil. These computations were compared with experimental data (obtained at Ames Research Center) which form part of the AGARD standard configuration for aeroelastic analysis. A variety of approximations to the full Navier-Stokes equations was used to determine the effect of frequency, shock wave motion, flow separation, and airfoil geometry on unsteady pressures and overall air loads. Good agreement is shown between experiment and theory with the limiting factor being the lack of a reliable turbulence model for high Reynolds number, unsteady transonic flows.
    Keywords: AERODYNAMICS
    Type: AGARD Transonic Unsteady Aerodyn. and its Aeroelastic Appl.; 22 p
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  • 10
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    Calculation of external-internal flow fields for mixed-compression inlets (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Supersonic inlet flows with mixed external-internal compressions were computed using a combined implicit-explicit (Beam-Warming-Steger/MacCormack) method for solving the three-dimensional unsteady, compressible Navier-Stokes equations in conservation form. Numerical calculations were made of various flows related to such inlet operations as the shock-wave intersections, subsonic spillage around the cowl lip, and inlet started versus unstarted conditions. Some of the computed results were compared with wind tunnel data.
    Keywords: AERODYNAMICS
    Type: NASA-TM-88362 , A-86409 , NAS 1.15:88362
    Format: application/pdf
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