Amplitude Annihilation in Wake-Influenced Aeroelastic Limit-Cycle Oscillations

This paper investigates the dynamics of a pitching and heaving aeroelastic wing undergoing large-amplitude limit-cycle oscillations influenced by a vortical wake from an upstream rectangular cylinder bluff body. The results show that under certain conditions, the limit cycle is annihilated. The conditions in which annihilation occurs are dependent on the limit-cycle frequency, bluff-body shedding frequency, and the magnitude of the mass coupling in the system. The low mass coupling configuration shows that vortical disturbances on the wing cause minor amplitude modulation until the shedding frequency is within a critical distance of the third harmonic of the limit-cycle oscillation frequency. Within this band, the amplitude modulations grow such that the pitch amplitude varies by up to 10 deg. When the mass coupling is increased and when the shedding frequency is within a critical distance of the third harmonic, the limit cycle is annihilated and the system returns to equilibrium. The annihilation phenomenon is caused by the addition of strong aerodynamic coupling between the vortex wake and the wing, influencing the limit-cycle kinematics such that the limit-cycle returns to the equilibrium position. The paper discusses both the kinematic and aerodynamic behaviors of wake-influenced aeroelastic limit-cycle annihilation.