The unsteady structure of two-dimensional steady laminar separation

Matthew D. Ripley, Laura Pauley

    Research output: Contribution to journalArticle

    81 Citations (Scopus)

    Abstract

    The two-dimensional unsteady incompressible Navier-Stokes equations, solved by a fractional time-step method, were used to investigate separation due to the application of an adverse pressure gradient to a low-Reynolds number boundary layer flow. The inviscid pressure distribution of Gaster [AGARD CP 4, 813 (1966)] was applied in the present computations to study the development of a laminar separation bubble. In all cases studied, periodic vortex shedding occurred from the primary separation region. The shed vortices initially lifted from the boundary layer and then returned towards the surface downstream. The shedding frequency nondimensionalized by the momentum thickness was found to be independent of Reynolds number. The value of the nondimensional Strouhal number, however, was found to differ from the results of Pauley et al. [J. Fluid Mech. 220, 397 (1990)], indicating that the shedding frequency varies with the nondimensional pressure distribution, Cp. The computational results were time averaged over several shedding cycles and the results were compared with Gaster. The numerical study accurately reproduced the major characteristics of the separation found in Gaster's study such as the separation point, the pressure plateau within the upstream portion of the separation bubble, and the reattachment point. The similarity between the experimental results and the time-averaged two-dimensional computational results indicates that the low-frequency velocity fluctuations detected by Gaster are primarily due to the motion of large vortex structures. This suggests that large-scale two-dimensional structures control bubble reattachment and small-scale turbulence contributes a secondary role.

    Original languageEnglish (US)
    Pages (from-to)3099-3106
    Number of pages8
    JournalPhysics of Fluids A
    Volume5
    Issue number12
    StatePublished - 1992

    Fingerprint

    bubbles
    pressure distribution
    Pressure distribution
    attachment
    Vortex flow
    Reynolds number
    vortices
    sheds
    Strouhal number
    vortex shedding
    boundary layer flow
    Boundary layer flow
    Vortex shedding
    low Reynolds number
    Pressure gradient
    pressure gradients
    Navier-Stokes equation
    upstream
    Navier Stokes equations
    boundary layers

    All Science Journal Classification (ASJC) codes

    • Condensed Matter Physics
    • Physics and Astronomy(all)
    • Mechanics of Materials
    • Computational Mechanics
    • Fluid Flow and Transfer Processes
    • Engineering(all)

    Cite this

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    abstract = "The two-dimensional unsteady incompressible Navier-Stokes equations, solved by a fractional time-step method, were used to investigate separation due to the application of an adverse pressure gradient to a low-Reynolds number boundary layer flow. The inviscid pressure distribution of Gaster [AGARD CP 4, 813 (1966)] was applied in the present computations to study the development of a laminar separation bubble. In all cases studied, periodic vortex shedding occurred from the primary separation region. The shed vortices initially lifted from the boundary layer and then returned towards the surface downstream. The shedding frequency nondimensionalized by the momentum thickness was found to be independent of Reynolds number. The value of the nondimensional Strouhal number, however, was found to differ from the results of Pauley et al. [J. Fluid Mech. 220, 397 (1990)], indicating that the shedding frequency varies with the nondimensional pressure distribution, Cp. The computational results were time averaged over several shedding cycles and the results were compared with Gaster. The numerical study accurately reproduced the major characteristics of the separation found in Gaster's study such as the separation point, the pressure plateau within the upstream portion of the separation bubble, and the reattachment point. The similarity between the experimental results and the time-averaged two-dimensional computational results indicates that the low-frequency velocity fluctuations detected by Gaster are primarily due to the motion of large vortex structures. This suggests that large-scale two-dimensional structures control bubble reattachment and small-scale turbulence contributes a secondary role.",
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    The unsteady structure of two-dimensional steady laminar separation. / Ripley, Matthew D.; Pauley, Laura.

    In: Physics of Fluids A, Vol. 5, No. 12, 1992, p. 3099-3106.

    Research output: Contribution to journalArticle

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    PY - 1992

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