Boundary layer separation singularities for an upstream moving wall

Dommelen, L. L. van; Shen, S. F.

doi:10.1007/bf01236354

Cited by 7 publications

(11 citation statements)

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“…However, on close examination the separation profile was found to exhibit a local maximum near the wall, and the growth of the boundary layer was found to be O(t s − t) −1/4 , matching that of the upstream-slipping singularity structure described by Van Dommelen & Shen (1982) and Elliott et al (1983). Nevertheless the downstream-slipping case has been of historical interest (Williams 1977), as well as being controversial, and local analyses have been carried out by Van Dommelen (1981) and Van Dommelen & Shen (1983) in an effort to describe such a structure. In addition, sketches of the anticipated streamline patterns expected near the singular structure have been given by Sears & Telionis (1975) and subsequently modified by Van Dommelen (1981).…”

Section: Introductionmentioning

confidence: 85%

Unsteady separation past moving surfaces

1998

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Unsteady boundary-layer development over moving walls in the limit of infinite Reynolds number is investigated using both the Eulerian and Lagrangian formulations. To illustrate general trends, two model problems are considered, namely the translating and rotating circular cylinder and a vortex convected in a uniform flow above an infinite flat plate. To enhance computational speed and accuracy for the Lagrangian formulation, a remeshing algorithm is developed. The calculated results show that unsteady separation is delayed with increasing wall speed and is eventually suppressed when the speed of the separation singularity approaches that of the local mainstream velocity. This suppression is also described analytically. Only 'upstreamslipping' separation is found to occur in the model problems. The changes in the topological features of the flow just prior to the separation that occur with increasing wall speed are discussed.

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Section: Introductionmentioning

confidence: 85%

Unsteady separation past moving surfaces

1998

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“…While this three-dimensional form of the MRS condition seems new, the general applicability of the two-dimensional case is fairly well established both theoretically (Moore 1958, Sears Rt Telionis 1975, Williams 1977, Shen 1978, Sychev 1979len Rt Shen 1980b, 1983a,b, Van Dommelen 1981 and experimentally (Ludwig 1964, Didden & Ho 1985.…”

Section: Y U = D D Y W = Omentioning

confidence: 99%

On the Lagrangian description of unsteady boundary-layer separation. Part 1. General theory

Dommelen

Cowley

1990

J. Fluid Mech.

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Asymptotic structhres for a number of unsteady three-dimensional separating flows follow and depend on the symmetry properties of the flow (e.g. line symmetry, axial symmetry).In the absence of any symmetry, the singularity structure just prior to separation is found to be quasi two-dimensional with a displacement thickness in the form of a crescent shaped ridge. Physically the singularities can be understood in terms of the behavior of a fluid element inside the boundary layer which contracts in a direction parallel to the boundary and expands normal to it, thus forcing the fluid above it to be ejected from the boundary layer.'Work funded under Space Act Agreement C99066G; presently at

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“…Part of the thickening of the boundary layer going towards separation from the upstream side is then due to additional streamlines coming from downstream that become part of the velocity profile. Van Dommelen & Shen (1983a) show that a self-consistent and reasonably complete mathematical description of their proposed flow exists in the non-interactive case. This description can explain the flattening of the velocity profile at flow reversal postulated in the MRS model.…”

Section: Introductionmentioning

confidence: 93%

“…The sketches on the left show streamlines and velocity profiles for a fixed wall, and those on the right for an upstream moving wall. Streamline profiles: (a) Moore (1958), (b) Sears & Telionis (1975), (c) Van Dommelen & Shen (1983a). (d) Velocity profiles as proposed by Sears & Telionis (1975).…”

Section: Introductionmentioning

confidence: 98%

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Numerical solution of unsteady boundary-layer separation in supersonic flow: upstream moving wall

Yapalparvi

Dommelen

2012

J. Fluid Mech.

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This paper is an extension of work on separation from a downstream moving wall by Ruban et al. (J. Fluid. Mech., vol. 678, 2011, pp. 124-155) and is in particular concerned with the boundary-layer separation in unsteady two-dimensional laminar supersonic flow. In a frame attached to the wall, the separation is assumed to be provoked by a shock wave impinging upon the boundary layer at a point that moves downstream with a non-dimensional speed which is assumed to be of order Re −1/8 where Re is the Reynolds number. In the coordinate system of the shock however, the wall moves upstream. The strength of the shock and its speed are allowed to vary with time on a characteristic time scale that is large compared to Re −1/4 . The 'triple-deck' model is used to describe the interaction process. The governing equations of the interaction problem can be derived from the Navier-Stokes equations in the limit Re → ∞. The numerical solutions are obtained using a combination of finite differences along the streamwise direction and Chebyshev collocation along the normal direction in conjunction with Newton linearization. In the present study with the wall moving upstream, the evidence is inconclusive regarding the so-called 'Moore-Rott-Sears' criterion being satisfied. Instead it is observed that the pressure rise from its initial value is very slow and that a recirculation region forms, the upstream part of which is wedge-shaped, as also observed in turbulent marginal separation for large values of angle of attack.

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Boundary layer separation singularities for an upstream moving wall

Cited by 7 publications

References 13 publications

Unsteady separation past moving surfaces

Unsteady separation past moving surfaces

On the Lagrangian description of unsteady boundary-layer separation. Part 1. General theory

Numerical solution of unsteady boundary-layer separation in supersonic flow: upstream moving wall

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