Aeroelastic response of an airfoil with structural and aerodynamic nonlinearities

The effects of structural and aerodynamic nonlinearities on the response of aeroelastic systems are examined for a typical airfoil section. Control surface freeplay is the source of the structural nonlinearity. Classical Theodorsen aerodynamic theory is combined with an appropriate structural theory to construct a nonlinear aeroelastic model that is used to simulate responses due to a prescribed angle of attack or gust loads. A companion wing tunnel experimental program using an aeroelastic airfoil model and a rotating slotted cylinder gust generator is used to validate the theoretical results. To study nonlinear aerodynamic effects, a computational fluid dynamics (CFD) method based upon Euler equations and developed at Duke is combined with a linear structural airfoil model to determine flutter and limit cycle oscillation (LCO) response for a wide range of structural parameters and Mach number. Finally, a system identification based reduced order aerodynamic model (ROM) is also presented. It will be useful when considering flutter and LCO of more complex wing planforms.