A Numerical Study of Unsteady Laminar Boundary Layer Separation
A Numerical Study of Unsteady Laminar Boundary Layer Separation

Author: Laura Lynn Pauley

Publisher:

Published: 1988

Total Pages: 222

ISBN-13:

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The unsteady, incompressible Navier-Stokes equations were solved using a fractional timestep method. Using this technique, the separation of a laminar boundary layer under the influence of an external adverse pressure gradient was.

Some Important Problem in Unsteady Boundary Layers Including Separation. I. Nature of Singularity on Oscillating Airfoils
Some Important Problem in Unsteady Boundary Layers Including Separation. I. Nature of Singularity on Oscillating Airfoils

Author: T. Cebeci

Publisher:

Published: 1984

Total Pages: 19

ISBN-13:

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Preliminary results are presented for the analysis of unsteady laminar boundary layers on oscillating airfoils. An examination of the evolution of the boundary layer near the nose of an oscillating airfoil has revealed that, when the reduced frequency is of the same order as in experiments on dynamic stall, the unsteady boundary layer ceases to behave in a smooth manner just downstream of separation and before one cycle is completed. As for the case of the implusively started circular cylinder, the irregular behavior signals the onset of a singularity in the solution of the boundary layer equations. Numerical results for the method are compared with the numerical results of van Dommelen and Shen for the impulsively started circular cylinder, the irregular behavior signals the onset of a singularity in the solution of the boundary layer equations. Numerical results for the method are compared with the numerical results of van Dommelen and Shen for the impulsively started circular cylinder.

On the Lagrangian Description of Unsteady Boundary Layer Separation. Part 1
On the Lagrangian Description of Unsteady Boundary Layer Separation. Part 1

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-09

Total Pages: 50

ISBN-13: 9781722455040

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Although unsteady, high-Reynolds number, laminar boundary layers have conventionally been studied in terms of Eulerian coordinates, a Lagrangian approach may have significant analytical and computational advantages. In Lagrangian coordinates the classical boundary layer equations decouple into a momentum equation for the motion parallel to the boundary, and a hyperbolic continuity equation (essentially a conserved Jacobian) for the motion normal to the boundary. The momentum equations, plus the energy equation if the flow is compressible, can be solved independently of the continuity equation. Unsteady separation occurs when the continuity equation becomes singular as a result of touching characteristics, the condition for which can be expressed in terms of the solution of the momentum equations. The solutions to the momentum and energy equations remain regular. Asymptotic structures for a number of unsteady 3-D separating flows follow and depend on the symmetry properties of the flow. In the absence of any symmetry, the singularity structure just prior to separation is found to be quasi 2-D 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. Vandommelen, Leon L. and Cowley, Stephen J. Glenn Research Center NASA-SAA-C-99066-G; RTOP 505-62-21...

Numerical Investigation of Unsteady Boundary-layer Separation
Numerical Investigation of Unsteady Boundary-layer Separation

Author: Demetri P. Telionis

Publisher:

Published: 1972

Total Pages: 24

ISBN-13:

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It has been previously indicated both theoretically and experimentally that for steady flow over moving boundaries, the vanishing of skin friction does not mean separation and that separation occurs at a station where the generalized Moore-Rott-Sears (MRS) criterion is satisfied. The authors have earlier indicated numerically that the Goldstein-type separation-singularity appears at the point where the MRS criterion is satisfied. In the present paper and in accordance with the theoretical work of Sears and one of the authors, this idea is extended to unsteady flows. A Goldstein-type of a traveling singularity is discovered and interpreted as 'unsteady boundary-layer separation.' The features of the flow in the neighborhood of this singularity are investigated. (Author).

Boundary-Layer Separation
Boundary-Layer Separation

Author: Frank T. Smith

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 403

ISBN-13: 3642830005

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The IUTAM Symposium on Boundary-Layer Separation, suggested by the UK National Committee of Theoretical and Applied Mechanics and supported by the International Union of Theoretical and Applied Mechanics, was held at University College London on August 26-28, 1986. The proposed theme and scope of the Symposium were designed to help to bring about the necessary interaction between experimentalists, computationalists and theoreticians for the furthering of understanding in this challenging subject. The talks and discussions were aimed at representing the very wide range and application of separating-flow phenomena, which often substantially affect the whole of fluid dynamics at medium to large Reynolds numbers, covering in particular both laminar and turbulent flow, steady or unsteady, two- or three-dimensional, small or large-scale, incompressible or compressible, external or internal, from the experimental, computational and theoretical standpoints. It was intended that about 80 scientists would participate in the Symposium, with about 25 talks being delivered, to which poster sessions with 8 contributions were added subsequently. All the speakers and poster presenters were selected by the scientific committee, although two late replacements of speakers were required. Fruitful discussions, well led by the session chairmen, took place formally after each talk and after the poster sessions and informally on other occasions including the social events. The present proceedings of the Symposium appear to reflect much of the current state of experimental, computational and theoretical work and progress in boundary-layer separation. We hope that they provide also ideas, questions and stimulation, in addition to major recent developments.