Aeroelastic tailoring of nonlinear typical section using the method of multiple scales to predict post-flutter stable LCOs

Most aeroelastic systems suffer from nonlinear behavior. The characterization of nonlinear response in aeroelastic systems is, therefore, a relevant issue. When designing for best performance, for instance, to expand the flutter boundaries, the nonlinear aeroelastic behavior is also a formidable challenge. Towards optimal aeroelastic tailoring, an alternative approach may be admitting acceptable levels when nonlinearities are present to the problem. To do this post-flutter behavior can be added to the optimization reasoning, along with the traditional flutter boundaries expansion. The current work proposes an investigation on the aeroelastic tailoring of a typical section with hardening nonlinearity in pitching stiffness seeking to expand the flutter onset boundary and minimum stable LCO amplitudes in post-flutter. This investigation uses the traditional typical section model to develop a reduced order model based on the multiple scales method viewing fast evaluations of the flutter onset and values of LCO amplitudes at some post-flutter airspeeds. Aeroelastic tailoring is based on the differential evolution algorithm to yield Pareto frontiers for the two selected objectives. An analysis of the design variables is presented, and the optimization results reveal that adequate compromise solutions can be assessed. Therefore, possible optimal post-flutter conditions for minimum LCO amplitudes can also be achieved.