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  • American Institute of Physics (AIP)  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of suction on the subharmonic instability of compressible boundary layers (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2179-2190 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of self-similar suction distributions on the subharmonic instability of a two-dimensional (2-D) compressible boundary layer over an insulated flat plate is analyzed using the Floquet model. The resulting problem is solved numerically by using finite differences. Results are presented for different Mach numbers. For supersonic flows results for first- and second-mode primary waves are presented. It is found that when the primary wave is a first mode, suction stabilizes the subharmonic wave at low and moderate Mach numbers. However, at high Mach numbers suction loses its effectiveness. When the primary wave is a second mode, suction is also found to stabilize the subharmonic mode. When the primary wave is a first mode merging with a second mode, the subharmonic wave is strongly destabilized by suction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857899
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  • 2
    Electronic Resource
    Electronic Resource
    Surface waves in closed basins under principal and autoparametric resonances (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1635-1648 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The method of multiple scales is used to analyze the nonlinear response of the surface of a liquid in a cylindrical container to a principal parametric resonant excitation in the presence of a two-to-one internal (autoparametric) resonance. Four autonomous first-order ordinary-differential equations are derived for the modulation of the amplitudes and phases of the two modes involved in the internal resonance when the higher mode is being excited by a principal parametric resonance. The modulation equations are used to determine the periodic oscillations and their stability. The force-response curves exhibit the jump and saturation phenomena as well as a Hopf bifurcation, whereas the frequency-response curves exhibit the jump phenomenon and supercritical and subcritical Hopf bifurcations. Limit-cycle solutions of the modulation equations are found between the Hopf frequencies; they correspond to aperiodic motions of the liquid surface. All limit cycles deform and lose stability by either pitchfork or cyclic-fold bifurcations as the excitation frequency or amplitude is varied. The pitchfork bifurcation breaks the symmetry of the limit cycles whereas the cyclic-fold bifurcation causes cyclic jumps, which may result in a transition to chaos. Period-three motions are found in a very narrow range of the excitation frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857571
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  • 3
    Electronic Resource
    Electronic Resource
    Subharmonic instability of compressible boundary layers (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1380-1392 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The subharmonic instability of a two-dimensional compressible boundary layer over an insulated flat plate is analyzed using the Floquet model. The resulting problem is solved numerically by using both finite differences and the computer code suport. Results are presented for subsonic, transonic, and supersonic flows. For supersonic flows results for the first and second modes are presented. The effects of Mach number, spanwise wave number, amplitude of the primary wave, Reynolds number, and frequency are studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857587
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  • 4
    Electronic Resource
    Electronic Resource
    Flow over bodies with suction through porous strips (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 2042-2053 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article addresses the steady, incompressible flow past a two-dimensional or an axisymmetric body with suction through porous strips. Closed-form solutions for each flow quantity are developed in the context of linearized triple-deck theory using Fourier transforms. To demonstrate the validity of these closed-form solutions, we compare the wall shear stress and pressure coefficients and the streamwise velocity profiles from the linearized theory are compared with those obtained by the numerical integration of both interacting and conventional boundary-layer equations. The agreement between the linearized triple-deck and interacting boundary-layer equations for the suction configurations proposed for laminar flow control is good; however, the conventional boundary layers, which fail to account for upstream influence, are shown to be in poor agreement with both interacting boundary layers and the linearized triple deck. Combining these linearized closed-form solutions with a perturbation scheme has enabled development of a simple linear optimization scheme to determine the number, spacing, and mass flow rate through the strips on two-dimensional and axisymmetric bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865590
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  • 5
    Electronic Resource
    Electronic Resource
    Acoustic receptivity of a boundary layer to Tollmien–Schlichting waves resulting from a finite-height hump at finite Reynolds numbers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3705-3716 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acoustic receptivity of a boundary layer to Tollmien–Schlichting (T–S) waves resulting from a finite-height hump at finite Reynolds numbers is investigated. The steady flow is calculated using an interacting boundary-layer (IBL) scheme that accounts for viscous/inviscid interactions. The unsteady flow is written as the sum of a Stokes wave and a traveling wave generated due to the interaction of the Stokes flow with the steady disturbance resulting from the hump. The traveling wave is governed by a set of nonhomogeneous equations, which is a generalization of the Orr–Sommerfeld equation. The solution of these nonhomogeneous equations is projected onto the quasiparallel eigenmode using the quasiparallel adjoint. This leads to a nonhomogeneous equation with variable coefficients governing the amplitude and phase of the T–S wave. Results are presented for the amplitude variation and the receptivity at finite Reynolds numbers. The results are in good agreement with the experimental results of Saric, Hoos, and Radeztsky [Boundary Layer Stability and Transition to Turbulence (ASME, New York, 1991), FED No. 114, pp. 17–22] for all tested hump heights at the two-tested sound pressure levels. Application of this paper's theory to small humps yields results that agree with those of Choudhari and Streett [Phys. Fluids A 4, 2495 (1992)], and Crouch [Phys. Fluids A 4, 1408 (1992)]. Application of suction is shown to reduce the receptivity resulting from the hump.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868361
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  • 6
    Electronic Resource
    Electronic Resource
    Laminar flow control of subsonic boundary layers by suction and heat-transfer strips (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1259-1272 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of suction and heat-transfer strips on the stability of subsonic boundary layers over flat plates are investigated. The mean flows are calculated by using interacting boundary layers. Then the linear two-dimensional quasiparallel spatial stability theory of compressible flows is used to calculate the growth rates and hence the amplification factors. Using the eN criterion, the optimal location of a suction strip for delaying transition is investigated. Moreover, using the fact that the incremental growth rates due to suction in subsonic flows vary linearly with suction velocity, influence coefficients are calculated that can be used to design "smart'' suction configurations. A major finding of the present investigation is the reversal of the effect of heating by strips compared with uniform heating. The present results show that a heating strip located near branch I of the neutral stability curve very much stabilizes the flow, in contrast with uniform heating, which destabilizes the flow. On the other hand, a cooling strip located near branch I of the neutral stability curve destabilizes the flow, in contrast with uniform cooling, which stabilizes the flow. It is also found that a properly placed cooling strip can delay transition in subsonic boundary layers. The optimal locations of heating and cooling strips are determined. The present findings may have important implications for the design of laminar flow control surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858244
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of heat transfer on the subharmonic instability of compressible boundary layers (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2148-2163 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of heat transfer on the subharmonic instability of a two-dimensional compressible boundary layer over a flat plate is analyzed using the Floquet model. The resulting problem is solved numerically by using both finite differences and the computer code suport. Results are presented for different Mach numbers. For supersonic flows, results for the first and second modes are presented. The results for an adiabatic flat plate are in good agreement with the results of the numerical simulations of Thumm et al. [in Laminar-Turbulent Transition, edited by D. Arnal and R. Michel (Springer-Verlag, Berlin, 1990), p. 271; (private communication)]. When the wall temperature is decreased and the primary wave is a second-mode wave, it is found that the subharmonic instability is shifted to higher frequencies and downstream locations. When the primary wave is a first-mode wave, the effect of cooling might be stabilizing or destabilizing depending on the frequency. When the primary wave is a first mode, cooling stabilizes the subharmonic wave at low spanwise wave numbers and destabilizes it at higher spanwise wave numbers. When the primary wave is either a first- or a second-mode wave, the most amplified subharmonic mode shifts toward a higher spanwise wave number as the cooling level increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857897
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of suction and wall shaping on the fundamental parametric resonance in boundary layers (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 963-974 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of self-similar as well as uniform-suction distributions on the primary and fundamental parametric spatial and temporal instabilities of incompressible flows over a flat plate are studied. The Floquet model is used to analyze the fundamental instability. This model is also used to analyze the effect of wall shaping on such instabilities. The mean-flow problems as well as the stability problems are solved using finite differences. The effects of suction and wall shaping are evaluated and discussed in relation to previous works. The relation between spatial and temporal fundamental instabilities is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858277
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  • 9
    Electronic Resource
    Electronic Resource
    Compressional wave propagation in liquid and/or gas saturated elastic porous media (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3045-3055 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Concepts from the theory of interacting continua are employed to develop constitutive relations for liquid and/or gas saturated elastic porous media. The model is formulated by defining intrinsic stress tensors and densities in terms of the partial stress tensors, partial densities, and actual volume fractions occupied by each component. It is assumed that the constitutive law for each component as a single continuum relates intrinsic pressure to intrinsic deformation. Relative motion between the constituents is allowed through simple Darcy-type expressions. The governing equations together with the constitutive relations are used to investigate the propagation of both harmonic and transient pulses. In general three modes of wave propagation exist. In the case of a transient pulse, these modes lead to a three-wave structure. Laplace transform techniques are used to derive closed-form solutions for transient loading for two limiting values of viscous coupling (i.e., weak viscous coupling, strong viscous coupling). Strong viscous coupling results in the coalescence of the three wave fronts into a single front. Solutions for the general case of transient loading are obtained by numerical inversion of the Laplace transforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337760
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