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  • 1
    Electronic Resource
    Electronic Resource
    Spatial simulation of instability control by periodic suction blowing (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2138-2147 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The applicability of active control by periodic suction blowing in spatially evolving plane Poiseuille flow is investigated by the direct simulation of the three-dimensional, incompressible Navier–Stokes equations. The results reveal that significant reductions in perturbation amplitudes can be obtained by a proper choice of the control wave amplitude and phase. The upstream influence of the control wave is shown to be confined to a region in the vicinity of the control slot with no apparent effect on the flow development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857896
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  • 2
    Electronic Resource
    Electronic Resource
    The role of stationary cross-flow vortices in boundary-layer transition on swept wings (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3442-3453 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial evolution of stationary cross-flow-vortex packets in a laminar boundary layer on a swept wing is computed by direct numerical simulation with the incompressible Navier–Stokes equations. Steady suction and blowing at the wing surface is used to generate disturbances that are periodic and equally spaced in the spanwise direction. The initiated disturbances become unstable and lead to distinct stages of instability evolution. Initially, each vortex packet undergoes a region of chordwise and spanwise linear independent growth; then the individual packets coalesce downstream and lead to spanwise wave adjustments and linear superposition of adjacent packets; finally, the vortex packets reach sufficiently large amplitudes in later stages of disturbance development to nonlinearly interact, which results in the rapid growth of the disturbances. In this later stage, the low-velocity fluid near the wing surface is lifted out into the boundary layer and rolled over the high-speed fluid in the direction of the positive spanwise velocity component. Highly inflectional chordwise and spanwise velocity profiles are recorded in this region. Previous studies have demonstrated that these inflectional profiles spawn the rapid growth of secondary instabilities, which lead to the catastrophic breakdown to turbulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868401
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  • 3
    Electronic Resource
    Electronic Resource
    Quadrature imposition of compatibility conditions in Chebyshev methods (1990)
    Springer
    Journal of scientific computing 5 (1990), S. 223-239 
    Details
    ISSN: 1573-7691
    Keywords: Chebyshev methods ; Neumann problems ; Navier-Stokes equations ; pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Often, in solving an elliptic equation with Neumann boundary conditions, a compatibility condition has to be imposed for well-posedness. This condition involves integrals of the forcing function. When pseudospectral Chebyshev methods are used to discretize the partial differential equation, these integrals have to be approximated by an appropriate quadrature formula. The Gauss-Chebyshev (or any variant of it, like the Gauss-Lobatto) formula cannot be used here since the integrals under consideration do not include the weight function. A natural candidate to be used in approximating the integrals is the Clenshaw-Curtis formula; however, we show in this article that this is the wrong choice and it may lead to divergence if time-dependent methods are used to march the solution to steady state. We develop, in this paper, the correct quadrature formula for these problems. This formula takes into account the degree of the polynomials involved. We show that this formula leads to a well-conditioned Chebyshev approximation to the differential equations and that the compatibility condition is automatically satisfied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089165
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial direct numerical simulation of boundary-layer transition mechanisms: Validation of PSE theory (1993)
    Springer
    Theoretical and computational fluid dynamics 4 (1993), S. 271-288 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A study of instabilities in incompressible boundary-layer flow on a flat plate is conducted by spatial direct numerical simulation (DNS) of the Navier-Stokes equations. Here, the DNS results are used to evaluate critically the results obtained using parabolized stability equations (PSE) theory and to study mechanisms associated with breakdown from laminar to turbulent flow. Three test cases are considered: two-dimensional Tollmien-Schlichting wave propagation, subharmonic instability breakdown, and oblique-wave breakdown. The instability modes predicted by PSE theory are in good quantitative agreement with the DNS results, except a small discrepancy is evident in the mean-flow distortion component of the two-dimensional test problem. This discrepancy is attributed to far-field boundary-condition differences. Both DNS and PSE theory results show several modal discrepancies when compared with the experiments of subharmonic breakdown. Computations that allow for a small adverse pressure gradient in the basic flow and a variation of the disturbance frequency result in better agreement with the experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418777
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  • 5
    Electronic Resource
    Electronic Resource
    Spectral methods and their implementation to solution of aerodynamic and fluid mechanic problemsBased on an invited lecture. (1987)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 7 (1987), S. 1159-1189 
    Details
    ISSN: 0271-2091
    Keywords: Spectral Method ; Collocation ; Computational Fluid Dynamics ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fundamental concepts underlying spectral collocation methods, especially pertaining to their use in the solution of partial differential equations, are outlined. Theoretical accuracy results are reviewed and compared with results from test problems. A number of practical aspects of the construction and use of spectral methods are detailed, along with several solution schemes which have found utility in applications of spectral methods to practical problems. Results from a few of the successful applications of spectral methods to problems of aerodynamic and fluid mechanic interest are then outlined, followed by a discussion of the problem areas in spectral methods and the current research under way to overcome these difficulties.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650071103
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  • 6
    Electronic Resource
    Electronic Resource
    A spectral multi-domain technique for viscous compressible reacting flows (1988)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 8 (1988), S. 1121-1134 
    Details
    ISSN: 0271-2091
    Keywords: Spectral multi-domain method ; Viscous compressible flow ; Shock waves ; Chemical kinetics ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The first application of a spectral multi-domain method for viscous compressible flow is presented. The method imposes a global flux balance condition at the interface so that high-order continuity of the solution is preserved. The global flux balance is imposed in terms of a spectral integral of the discrete equations across adjoining domains. Since the discretized equations interior to each domain are solved uncoupled from each other and since the interface relation has a block structure, the solution scheme can be adapted to the particular requirement in each subdomain. To illustrate these advantages a Mach 11 shock calculation is presented to study the chemical kinetics initiated as air passes through a fully resolved shock wave.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650081002
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  • 7
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    Spatial direct numerical simulation of boundary-layer transition mechanisms: Validation of PSE theory (1993)
    Springer
    Details
    Publication Date: 1993-09-01
    Print ISSN: 0935-4964
    Electronic ISSN: 1432-2250
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 8
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    Spatial simulation of instability control by periodic suction blowing (1991)
    American Institute of Physics
    Details
    Publication Date: 1991-09-01
    Print ISSN: 0899-8213
    Topics: Physics
    Published by American Institute of Physics
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  • 9
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    The role of stationary cross‐flow vortices in boundary‐layer transition on swept wings (1994)
    American Institute of Physics
    Details
    Publication Date: 1994-10-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Spatial simulation of secondary instability in plane channel flow: comparison of K- and H-type disturbances (1993)
    Cambridge University Press
    Details
    Publication Date: 1993-08-01
    Description: This study involves a numerical simulation of spatially evolving secondary instability in plane channel flow. The computational algorithm integrates the time-dependent, three-dimensional, incompressible Navier-Stokes equations by a mixed finite-difference/spectral technique. In particular, we are interested in the differences between instabilities instigated by Klebanoff (K-) type and Herbert (H-) type inflow conditions, and in comparing the present spatial results with previous temporal models. It is found that for the present inflow conditions, H-type instability is biased towards one of the channel walls, while K-type instability evolves on both walls. For low initial perturbation amplitudes, H-type instability exhibits higher growth rates than K-type instability while higher initial amplitudes lead to comparable growth rates of both Hand K-type instability. In H-type instability, spectral analysis reveals the presence of the subharmonic two-dimensional mode which promotes the growth of the three-dimensional spanwise and fundamental modes through nonlinear interactions. An intermodal energy transfer study demonstrates that there is a net energy transfer from the three-dimensional modes to the two-dimensional mode. This analysis also indicates that the mean mode transfers net energy to the two-dimensional subharmonic mode and to the three-dimensional modes. © 1993, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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