Accession Number : ADA138725

Title :   The Unsteady Boundary Layer on an Elliptic Cylinder Following the Impulsive Onset of Translational and Rotational Motion.

Descriptive Note : Interim rept.,


Personal Author(s) : Billings,D F ; Chow,C Y

PDF Url : ADA138725

Report Date : 13 Jan 1983

Pagination or Media Count : 10

Abstract : The fluid motion about an elliptic cylinder impulsively set into translational and rotational motion is obtained by the method of matched asymptotic expansions for small time and large Reynolds number. The constraint of the perturbation model is that the boundary layer thickness and the distance of travel are of the same asymptotic order. It is found that pitch-up motion or rotation accompanying translation at an angle of attack is indeed capable of preventing the early formation of a leading edge separation bubble. Even before evident in the streamline pattern, the incipient separation bubble is accompanied by a characteristic vorticity signature in the vicinity of the leading edge that is quite different from that with rotation. Further, the onset of an adverse pressure gradient is displaced rearward from its location for pure translation. The pre-Kutta condition lift evidently arises with the local acceleration that is a consequence of the displacement effect of the growing boundary layer. (Author)

Descriptors :   *Boundary layer flow, Cylindrical bodies, Rotation, Motion, Unsteady flow, Angle of attack, Airfoils, Flow separation, Perturbation theory

Subject Categories : Aircraft
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE