A nonlinear analysis of stability and gust response of aeroelastic systems

In this paper, the mechanism of limit-cycle excitation is investigated for an aeroelastic system with structural nonlinearities. The analysis is performed on a simplified aeroelastic model retaining only two structural modes (first bending and first torsional modes) and with a simplified description of both unsteady loads due to wing oscillation and external gust excitation. Two cases are considered, without and with gust excitation. In the first case, normal form analysis is employed to give an approximation of the basin of attraction of stable limit cycles in the space of initial conditions. In the second case, a critical gust intensity for a given gust gradient leading again to undamped oscillations is identified.