Identification of nonlinear aeroelastic behavior of a wing with pitching and plunging freeplay via higher-order spectra analysis

Higher-order spectra (HOS) analysis is utilized to analyze the nonlinear utter aspects of the AGARD 445.6 wing with pitching and plunging freeplay nonlinearities installed at the root. High-fidelity fluid-structure interaction simulations are conducted and the transient responses are monitored at the root and tip of the wing. The transient responses are truncated such that only the static portion of the signal remains and and the HOS are evaluated. The pitching/plunging freeplay ranges of motion and initial setting angle are varied, and the effect on nonlinear interactions and transient response are monitored. It is demonstrated that the presence of pitching freeplay is a major driver in the nonlinear phenomena, that the amplitude of the LCO is highly sensitive to the plunging freeplay range of motion whilst the presence of nonlinear interactions are dependent on interactions between the pitching and plunging freeplay effects. The application of this methodology from a practical perspective includes structural health monitoring, and the ability to identify and mitigate undesirable nonlinear aeroelastic phenomena in the design phase.