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  • 1
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    Numerical investigation of unsteady inlet flowfields (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 25; 75-81
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  • 2
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    Numerical simulation of self-excited oscillations in a ramjet inlet-diffuser flow (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper describes numerical simulations of self-excited oscillations in a two-dimensional transonic inlet-diffuser flow by solving the Navier-Stokes equations with a two-equation turbulence model. The calculated amplitudes of oscillations for the terminal shock and the velocity fields compare well with experimental measurements; however, the predicted frequency of oscillations is about 50 percent higher. The formation of a pair of downstream-traveling, counter-rotating vortices at each cycle of velocity fluctuations, as reported experimentally, is vividly revealed by the numerical results.
    Keywords: AERODYNAMICS
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  • 3
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    Ramjet diffuser flowfield response to large-amplitude combustor pressure oscillations (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 3; 472-477
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  • 4
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    Unsteady separated boundary layer in a transonic diffuser flow with self-excited oscillations (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A numerical investigation of two-dimensional unsteady boundary layer in a transonic diffuser flow with self-excited oscillations and strong flow separation by solving the compressible, Reynolds-averaged, thin-layer Navier-Stokes equations with two-equations turbulence model is described. Three different meshes with constant streamwise mesh distribution and varying vertical mesh distribution were used. Results obtained indicate that a refinement of mesh studied here has minimal effect on the mean boundary layer flow but significantly increases the amplitude of oscillation of all flow variables. Comparisons of unsteady wall pressure, velocity profile, terminal shock, and separation pocket among computations and with experiment are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-1037
    Format: text
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  • 5
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    Numerical Investigation of unsteady inlet flow fields (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The flow field within an unsteady, two-dimensional inlet is studied numerically, using a two dimensional Navier Stokes and a one-dimensional inviscid model. Unsteadiness is introduced by varying the outflow pressure boundary condition. The cases considered include outflow pressure variations which were a single pressure pulse, a rapid increase and a sine function. The amplitude of the imposed exit plane pressure disturbance varied between 1 percent and 20 percent of the mean exit pressure. At the higher levels of pressure fluctuation, the viscous flow field results bore little resemblance to the inviscid ones. The viscous solution included such phenomena as shock trains and bifurcating separation pockets. The induced velocity at the outflow plane predicted by the viscous model differs significantly from accoustical theory or small perturbation results.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-0031
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  • 6
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    Downstream boundary effects on the frequency of self-excited oscillations in transonic diffuser flows (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An investigation of downstream boundary effects on the frequency of self-excited oscillations in two-dimensional, separated transonic diffuser flows has been conducted numerically by solving the compressible, Reynolds-averaged, thin-layer Navier-Stokes equation with a two-equation turbulence model. It was found that the unsteady diffuser flowfields are very sensitive to the location of the downstream boundary. Extension of the diffuser downstream boundary significantly reduces the frequency and amplitude of oscillations for pressure, velocity and shock. Computational results suggest that the mechanism causing the self-excited oscillation changes from viscous convective wave dominated oscillations to inviscid acoustic wave dominated oscillations when the location of downstream boundary varies from 8.66 to 134.7 throat height. The existence of a suction slot in the experimental setup obscures the physical downstream boundary and, therefore, presents a difficulty for quantitative comparisons between computation and experiment.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0161
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  • 7
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    A comparison between implicit and hybrid methods for the calculation of steady and unsteady inlet flows (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Numerical simulation of steady and unsteady transonic diffuser flows using two different computer codes are discussed and compared with experimental data. The codes solve the Reynolds-averaged, compressible, Navier-Stokes equations using various turbulence models. One of the codes has been applied extensively to diffuser flows and uses the hybrid method of MacCormack. This code is relatively inefficient numerically. The second code, which was developed more recently, is fully implicit and is relatively efficient numerically. Simulations of steady flows using the implicit code are shown to be in good agreement with simulations using the hybrid code. Both simulations are in good agreement with experimental results. Simulations of unsteady flows using the two codes are in good qualitative agreement with each other, although the quantitative agreement is not as good as in the steady flow cases. The implicit code is shown to be eight times faster than the hybrid code for unsteady flow calculations and up to 32 times faster for steady flow calculations. Results of calculations using alternative turbulence models are also discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-1125
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  • 8
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    Numerical simulation of a ramjet inlet flowfield in response to large amplitude combustor pressure oscillation (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The unsteady flow of a two-dimensional ramjet inlet is studied numerically by solving the Navier-Stokes equation with a two-equation turbulence model. Unsteadiness is introduced by prescribing the pressure disturbance at the inlet exit plane. The case with a sinusoidal exit plane pressure fluctuation of 20 percent of the steady exit pressure is considered. The resulting flow field exhibits a complicated interaction between the terminal shock, separation pockets and core flow. The exit plane properties feature a non-linear response to the imposed sinusoidal pressure variation.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-1363
    Format: text
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