The push towards lighter and more efficient aircraft structures has led to modern aircraft configurations that are more elastic than ever, featuring large elastic deformations in their operating conditions. This trend applies to UAV platforms as well as to transport aircraft. Such platform might be susceptible to detrimental aeroelastic phenomena that must be accurately analyzed and accounted for in the design process. One shortcoming of modern production aeroelastic analysis and design methods is that they typically rely on linear structural and linear aerodynamic models, which are not suitable for geometrically nonlinear structures, of large deformations.
The current study employs a nonlinear, modal-based, structural modeling approach, together with nonlinear aerodynamic modeling, for static aeroelastic analyses. The nonlinear structural model, intended for geometrically nonlinear structures of large deformations, analyzes the deformations of a beam-like structure by dividing it into a small number of segments. Large deformations are treated as the sum of large, rigid-body displacements of the segment, plus small, linear, elastic deformation within the segment. The nonlinear aerodynamic modeling approach is a modified strip theory, also designed for beam-like structures, that is based on a database of nonlinear sectional aerodynamic forces. The seminar will present the two models, with focus on the nonlinear structural model and the intricacies of the application of compatibility equations between segments when using a modal approach.
The numerical examples include several load cases that validate the implementation of the methodology and demonstrate its use for static aeroelastic applications. Two validation cases include a beam subject to a large follower tip force, with reference to results from commercial nonlinear finite-element solver, and a wind-tunnel test of a wing with large deformations. The third case is of a highly elastic wing subject to large aerodynamic loading. It is used to compare between the nonlinear and linear structural and aerodynamic modeling approaches, and highlight the effect of nonlinear modeling on the resulting aeroelastic and aerodynamic characteristics.