A Computational Investigation of Wake-Induced AirFoil Flutter in Incompressible Flow and Active Flutter Control
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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In this thesis several incompressible oscillatory flow and flutter problems were investigated. A previously developed unsteady panel code for single airfoil bending torsion flutter analysis was compared to Theodorsens classical theory. The panel code agrees with Theodorsens bending-torsion flutter analysis for natural frequency ratios Omega sub hOmega sub alpha less than 1.2. Also, a two airfoil unsteady panel code was modified for one degree of freedom flutter analysis. Code verification was completed by first comparing flat plate theory to the unsteady aerodynamic force and moment coefficients and then using the equation of motion to determine regions of instability. The possibility of active flutter control was investigated by positioning a small control airfoil in front of a neutrally stable reference airfoil. Results show that the flutter boundary may be changed through the placement, oscillation or scaling of a second airfoil upstream. A comparison with pitch damping curves published by Loewy confirms that the code is capable of predicting wake-induced airfoil flutter. Flutter, Wake-induced flutter, Active flutter control, Theodorsen comparison, Unsteady panel methods.