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Aerodynamic Theory for a Cascade of Oscillating Airfoils in Compressible Subsonic Flow.
Interim rept. 1 Jul-31 Dec 74,
TEXAS ENGINEERING EXPERIMENT STATION COLLEGE STATION
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A simple numerical technique is developed for determining the airload coefficients on a typical airfoil of the cascade. The effects of varying airfoil spacing, frequency, Mach number and phase difference between adjacent blades are investigated. In particular, the variations in the aerodynamic damping for pure vertical translational and pitching motions are considered. It is shown that translational damping can become zero but never negative at certain discrete frequencies. Furthermore, the results indicate that the pitching moment aerodynamic damping referred to the quarter-chord axis, while also being zero at the critical frequencies, can be negative at the higher Mach numbers over a wide range of frequencies of interest in flutter analysis. The effects of varying the stagger angle of the cascade are not considered in the present paper.
APPROVED FOR PUBLIC RELEASE