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.

Scientific and Technical Aerospace Reports
Scientific and Technical Aerospace Reports

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Publisher:

Published: 1988

Total Pages: 666

ISBN-13:

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Some Important Problems in Unsteady Boundary Layers Including Separation. II. Unsteady Boundary Layers Close to the Stagnation Region of Slender Bodies
Some Important Problems in Unsteady Boundary Layers Including Separation. II. Unsteady Boundary Layers Close to the Stagnation Region of Slender Bodies

Author: T. Cebeci

Publisher:

Published: 1984

Total Pages: 39

ISBN-13:

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The evolution of unsteady boundary layers on the plane of symmetry of a slender prolate spheroid in uniform motion at constant angle of attack after an impulsive start has been studied for the case of prescribed pressure distribution. Calculated results have been obtained for angles of attack ranging from 30 degrees to 50 degrees and show, for example, that the unsteady-state solutions approach the steady-state solutions rapidly on the windward and leeward sides for alpha and alpha sub c (approximately - 41 degrees). This is also so on the windward side for alpha alpha sub c. On the leeward side for alpha> and alpha sub c, however, the unsteady boundary layer is initially unseparated but develops a region of reversed flow with increasing time. Subsequently, the streamwise displacement thickness develops a pronounced peak which leads to a singularity of the type observed by van Dommelen and Shen on a circular cylinder started impulsively from rest. (Author).

Aeronautical Engineering
Aeronautical Engineering

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Publisher:

Published: 1988

Total Pages: 554

ISBN-13:

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A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA).