Computational Study of Aeroelastic Limit Cycles due to Localized Structural Nonlinearities

Abstract

Aeroelastic systems including all-moving control surfaces and aircraft wings with stores may experience limit cycling caused by nonlinear structural and/or aerodynamic mechanisms. These systems are examined here via two different and complementary models, with nonlinear wing-root and nonlinear wing-store attachments, respectively, subjected to linear potential flow aerodynamic forces. Limit-cycle responses are obtained through an efficient computational method based on harmonic balance by using the spatially localized (hence mathematically separable) nature of the assumed nonlinearities. Results pertaining to a cubic hardening or softening restoring force in stiffness or damping, freeplay, and Coulomb friction are discussed along with confirmatory time-marching responses for selected cases. Clear relationships are established between the linear flutter behavior and the limit-cycle responses corresponding to each nonlinearity. Overall, this work provides an improved understanding, as compared to prior work, of the beneficial and/or detrimental effects of various localized nonlinearities on the aeroelastic response of all-moving control surfaces and store-carrying aircraft wings.