Accession Number : ADP004162

Title :   Unsteady Aerodynamic Loading of an Airfoil due to Vortices Released Intermittently from Its Upper Surface,

Corporate Author : COLORADO UNIV AT BOULDER

Personal Author(s) : Chow,C. Y. ; Chiu,C. S.

Report Date : 1984

Pagination or Media Count : 6

Abstract : An unsteady flow analysis is made of the flow past a symmetric airfoil with identical vortices released intermittently from its upper surface. The vortex train is used to simulate the flow observed in the laboratory which was perturbed by an oscillating spoiler or a rotating cam embedded in the airfoil surface. Based on numerical computations, the airfoil lift has a general behavior that it increases oscillatorily with time, and seems to approach an asymptotic value as time increases indefinitely. The asymptotic lift is enhanced with increasing frequency as which vortices are generated, and is only slightly influenced by changing the vortex-releasing position along the chord. The behavior of the drag is similar to that of the lift, but its magnitude is two orders smaller. Our study also indicates that it is more efficient to implement the vortex-augmented unsteady lift at higher angles of attack of airfoil. (Author)

Descriptors :   *Aerodynamic loading, *Unsteady flow, Vortices, Airfoils, Symmetry, Perturbations, Numerical analysis, Vortex shedding, Cams, Rotation, Spoilers, Oscillation, Aerodynamic lift, Asymptotic series, Augmentation, Aerodynamic drag, Angle of attack

Distribution Statement : APPROVED FOR PUBLIC RELEASE