| In this research we consider three aeroelastic systems of a single airfoil, two airfoils and a periodically connected cascade of 10 identical airfoils such as those in turbines or compressors. These airfoils are elastically suspended and oscillate in the fluid flow. For velocities of the fluid flow below critical, oscillations decay. When velocity is above critical, oscillations blow up. This aerodynamic instability is called flutter.; Considerable amount of research has been done on flutter boundaries prediction. It is known to be well described by linear models. However little is known about the effects of nonlinearities on a flutter instability. These effects can be dangerous. For instance, the system might become unstable for velocities below flutter, whereas classical linear models predict stability.; In this work we show nature of nonlinear mechanisms and investigate their dynamics. To achieve the goals we develop multi-dimensional computer simulations and Reduced Order Models in the form of ODES. The latter are amenable to analytic explorations.; We perform extensive nonlinear analysis for a single airfoil problem and find numerous examples contradicting existing hypothesis on nonlinear flutter. We show that for a two blade problem the nonlinear flutter can be dynamically very rich, with 132 regimes possible. This, we envision, can be utilized in fluid control problems. Finally, for a cascade we show that nonlinear behavior typically falls into just two cases, which are possible for any types of nonlinear springs. |
