Limit-cycle oscillations in high-aspect-ratio wings

The paper presents results obtained for limit-cycle oscillations (LCOs) in high-aspect-ratio wings caused by structural and aerodynamic nonlinearities . The analysis is based on geometrically exact structural analysis and fini te-state unsteady aerodynamics with stall. The results indicate that stall limits the amplitude of post-flutter unstable oscillations. At speeds below the linear flutter speed, LCOs can be observed if the stable steady state is disturbed by a finite-amplitude disturbance. A critical disturbance magn itude is required at a given speed and a critical speed is required at a gi ven disturbance magnitude to initiate LCOs. The LCO initiation mechanism ca n be attributed to the change in structural characteristics of the wing wit h deformation. It is also observed that the LCO gets increasingly complex w ith increasing speed. Period doubling is observed at low speeds and as the speed increases the oscillations lose periodicity and become chaotic. (C) 2 001 Academic Press.