Nonlinear Aeroelasticity

The nonlinear behavior and flutter characteristics of an aeroelastic system with control surface freeplay provides a platform for studying some interesting behavior. A low-order, state-space numerical model of the aeroelastic typical section was created which allows for the inclusion of structural freeplay and preload in the control surface degree of freedom. A physical model of the system was also constructed for use in the Duke University low-speed wind tunnel.


One of the most interesting aspects of the behavior of the airfoil is that hysteresis (between types of limit cycle behavior) is present. That is, the type of (flutter) response and the flow speeds at which they occur depends on whether the flow rate is increasing or decreasing. This is nicely captured by the spectrograms shown below.

More details of this research can be found in the paper published in the Royal Society in 2002.