Unsteady aeroelastic behaviors of rigid airfoils with preset angles of attack

The effects of varying the angle of attack on the flutter speed and limit cycle oscillations of an aeroelastic system are investigated. This system consists of a plunging and pitching rigid airfoil supported by linear springs. The unsteady vortex lattice method is used to model the unsteady flow. The objective is to determine how the flutter boundary is affected by changing the angle of attack. To solve simultaneously and interactively the governing equations, an iterative scheme based on Hamming's fourth order predictor-corrector model is employed. Several numerical simulations are conducted for various angles of attack to determine their effects on the dynamic behavior of the aeroelastic system and particularly on the dynamic stability or flutter speed and the nonlinear response of the system. The results show that the flutter speed increases as the angle of attack is increased. It is also determined that increasing the preset angle of attack results in a decrease in the dynamic amplitudes of the nonlinear response. In other words, increasing the angle of attack offers a way to control the system in terms of delaying flutter and reducing the limit-cycle oscillations amplitudes.