Aeroelastic Stability Analysis of Tailored Pretwisted Wings

In this paper, the aeroelastic stability of a tailored aircraft wing with different pretwist distributions is investigated. The structure of the wing is modeled using the geometrically exact fully intrinsic beam theory of Hodges, whereas the aerodynamic loads are simulated by an incompressible unsteady aerodynamic model. The governing nonlinear partial differential equations are discretized using a time-space scheme, and the stability of the system is sought by evaluating the eigenvalues of the linearized system. The wings have linear or quadratic pretwist distributions, and the effect of various twist angles on isotropic and tailored wings is investigated. In this study, the effect of pretwist is considered on both the aerodynamic and structural models. Moreover, the effect of wing structure taper ratio in conjunction with the pretwist is investigated. The preliminary results obtained for a wing modeled as a clamped-free beam are compared with those reported in the literature and excellent agreement is observed. It is concluded that the pretwist angle leads to mode coupling and also has a significant effect on the flutter speed of the wing. By pretwisting the wing, the flutter speed of the wing with respect to the clean wing increases until a specific twist value and then decreases. Moreover, adding the pretwist to the wing decreases the flutter frequency. Finally, results highlighting the effect of bend-twist elastic coupling and wing taper ratio in combination with the pretwist angle on the aeroelastic stability of the wing are provided.