Aeroelastic systems are those that involve the coupled interaction between a convecting fluid and a flexible elastic structure. The nonlinear dynamical response of such systems is of great current interest. Existing aircraft are known to encounter limit cycle oscillations (LCO) in certain flight regimes, and relatively simple experimental wind tunnel models have been designed to exhibit LCO as well. In the present paper, the results of these wind tunnel experiments are discussed and compared to comparable results from mathematical models. The physical models include (1) an airfoil and a control surface attached with an elastic spring including free-play and (2) a delta wing with elastic geometrical nonlinearities due to bending and torsional deformations. Both self-excited oscillations such as flutter and LCO, as well as forced oscillations due to an aerodynamic gust, are discussed. The advantages of representing the unsteady aerodynamic flow field in terms of global modes for such studies are emphasized and illustrated.

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