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  • 1
    Electronic Resource
    Electronic Resource
    The velocity field created by a shallow bump in a boundary layer (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3079-3085 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of measurements of the disturbance velocity field generated in a boundary layer by a shallow three-dimensional bump oscillating at a very low frequency on the surface of a flat plate are reported. The disturbance was entirely confined to the boundary layer. Profiles of the mean velocity, the disturbance velocity at the fundamental frequency, and at the first harmonic are presented. These profiles were measured both upstream and downstream of the oscillating bump. About 100 boundary layer thicknesses downstream of the bump the intensity had a maximum near η=2, with a magnitude of about 0.2%. Measurements of the disturbance velocity were also made at various spanwise and downstream locations at a fixed distance from the boundary of one displacement thickness. The spanwise profiles of the disturbance field changed dramatically from the near-field region of the bump to the far downstream region. Finally, the spanwise spectrum of the disturbances at three locations downstream of the bump are presented. The spanwise spectrum of the disturbance showed a primary peak consistent with the motion and geometry of the driver. This peak decreased slowly with downstream distance. In addition, a small secondary peak in the spanwise spectrum was apparent near the bump. This peak increased rapidly with downstream distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868132
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of turbulence with a detonation wave (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 745-749 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper addresses a specific reactive-flow configuration, namely, the interaction of a detonation wave with convected homogeneous isotropic weak turbulence (which can be constructed by a Fourier synthesis of small-amplitude vorticity waves). The effect of chemical heat release on the rms fluctuations downstream of the detonation is presented as a function of Mach number. In addition, for the particular case of the von Kármán spectrum, the one-dimensional power spectra of these flow quantities are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858657
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  • 3
    Electronic Resource
    Electronic Resource
    Absolute–convective instabilities and their associated wave packets in a compressible reacting mixing layer (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 901-915 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the transition from convective to absolute instability in a reacting compressible mixing layer with finite rate chemistry is examined. The reaction is assumed to be one step, irreversible, and of Arrhenius type. It is shown that absolute instability can exist for moderate heat release without backflow. The effects of the temperature ratio, heat release parameter, Zeldovich number, equivalence ratio, direction of propagation of the disturbances, and the Mach number on the transition value of the velocity ratio are given. The present results are compared to those obtained from the flame sheet model for the temperature using the Lock similarity solution for the velocity profile. Finally, the structure of the wave packets produced by an impulse in the absolutely unstable flow is examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858636
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  • 4
    Electronic Resource
    Electronic Resource
    The structure of variable property, compressible mixing layers in binary gas mixtures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 1945-1953 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all 30 combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of 8 and the Prandtl number by a factor of 2 across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869103
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  • 5
    Electronic Resource
    Electronic Resource
    Erratum: "Temperature and suction effects on the instability of an infinite swept attachment line'' [Phys. Fluids A 4, 2008 (1992)] (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 286-286 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858786
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  • 6
    Electronic Resource
    Electronic Resource
    Absolute/convective instabilities and the convective Mach number in a compressible mixing layer (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 949-954 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper two aspects of the stability of a compressible mixing layer are considered: absolute/convective instability and the convective Mach number. It is shown that, for Mach numbers less than unity, the compressible mixing layer is convectively unstable unless there is an appreciable amount of backflow. A rigorous derivation of a convective Mach number based on linear stability theory for the flow of a multispecies gas in a mixing layer is also presented. In particular, the definition is based on the free-stream Mach number in the laboratory frame and is independent of the speed of the large-scale structures and the speed of the most unstable wave. The result is compared with the heuristic definitions of others and to selected experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857655
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  • 7
    Electronic Resource
    Electronic Resource
    The stability of compressible mixing layers in binary gases (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 1954-1963 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of a study of the inviscid two-dimensional spatial stability of a parallel compressible mixing layer in a binary gas. The parameters of this study are the Mach number of the fast stream, the ratio of the velocity of the slow stream to that of the fast stream, the ratio of the temperatures, the composition of the gas in the slow stream and in the fast stream, and the frequency of the disturbance wave. The ratio of the molecular weight of the slow stream to that of the fast stream is found to be an important quantity and is used as an independent variable in presenting the stability characteristics of the flow. It is shown that differing molecular weights have a significant effect on the neutral-mode phase speeds, the phase speeds of the unstable modes, the maximum growth rates, and the unstable frequency range of the disturbances. The molecular weight ratio is a reasonable predictor of the stability trends. We have further demonstrated that the normalized growth rate as a function of the convective Mach number is relatively insensitive (≈25%) to changes in the composition of the mixing layer. Thus, the normalized growth rate is a key element when considering the stability of compressible mixing layers, since once the basic stability characteristics for a particular combination of gases is known at zero Mach number, the decrease in growth rates due to compressibility effects at the larger convective Mach numbers is somewhat predictable. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868974
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  • 8
    Electronic Resource
    Electronic Resource
    Induced Mach wave–flame interactions in laminar supersonic fuel jets (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 422-427 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model problem is proposed to investigate the steady response of a reacting, compressible laminar jet to Mach waves generated by wavy walls in a channel of finite width. The model consists of a two-dimensional jet of fuel emerging into a stream of oxidizer which are allowed to mix and react in the presence of the Mach waves. The governing equations are taken to be the steady parabolized Navier–Stokes equations which are solved numerically. The kinetics is assumed to be a one-step, irreversible reaction of the Arrhenius type. Two important questions on the Mach wave–flame interactions are discussed: (i) how is the flame structure altered by the presence of the Mach waves, and (ii) can the presence of the Mach waves change the efficiency of the combustion processes?
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858865
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  • 9
    Electronic Resource
    Electronic Resource
    Nonlinear interaction of a detonation/vorticity wave (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1972-1979 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction of an oblique, overdriven detonation wave with a vorticity disturbance is investigated by a direct two-dimensional numerical simulation using a multidomain, finite-difference solution of the compressible Euler equations. The results are compared to those of linear theory, which predict that the effect of exothermicity on the interaction is relatively small except possibly near a critical angle where linear theory no longer holds. It is found that the steady-state computational results whenever obtained in this study agree with the results of linear theory. However, for cases with incident angle near the critical angle, moderate disturbance amplitudes, and/or sudden transient encounter with a disturbance, the effects of exothermicity are more pronounced than predicted by linear theory. Finally, it is found that linear theory correctly determines the critical angle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857928
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  • 10
    Electronic Resource
    Electronic Resource
    Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 3087-3097 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the ignition and structure of a reacting compressible mixing layer lying between two streams of reactants with different free-stream speeds and temperatures using finite rate chemistry are considered. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. In particular, for sufficiently large Zeldovich number, the three regimes first described by Linan and Crespo [Combust. Sci. Technol. 14, 95 (1976)]; i.e., ignition, deflagration, and diffusion flame, occur in supersonic as well as in subsonic flows. An analysis of both the ignition and diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows an analysis of the behavior of these regimes as a function of the parameters of the problem. For the ignition regime, a well-defined ignition point will always exist provided the adiabatic flame temperature is greater than either free-stream temperature. For the diffusion flame regime, the location of the flame changes significantly with changes in the equivalence ratio and the Schmidt numbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857853
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