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Aeroelastic modeling and analysis of high aspect ratio wings with different fidelity structural models

Çiçek, Gökçen.
The focus of this study is in the area of static aeroelasticity, and it is concerned with modeling and analysis of high aspect ratio wings experiencing large torsional deflections. In this study, the effects of different fidelity structural models on static aeroelasticity are investigated. Preference of light and flexible structures due to performance and weight criteria and certification requirements make the aeroelastic analysis more and more essential for aircraft. Especially for the preliminary design phase, simple models are preferred to reduce the computational time and to perform the design iterations. Such a study is important in order to obtain aeroelastically efficient structure and integrate aeroelastic concepts at the preliminary design stage without making analysis complicated. The research approach adopted in this thesis includes loosely coupled structural and aerodynamic models. The approach for the structural modeling presented here is based on both linear and nonlinear structural theories. The linear structural theory is based on bending-torsion beam finite element formulations. The nonlinear theory is based on the nonlinear finite element model with only torsional rotation degree of freedom to study specifically the static aeroelastic behavior. The aerodynamic theories used for the aeroelastic coupling are lifting line theory and lifting surface theory which is based on Multhopp-Richardson’s solution to provide the spanwise loading of lifting surfaces with camber and twist. The focus of the thesis study is on divergence, one of the most important aeroelastic phenomenon. Analyses are performed by coupling the two different structural models with the lifting line theory and lifting surface theory to perform the divergence analysis of a simple plate-like wing model. Significant differences are observed between the linear and the nonlinear solution methodologies in terms of torsional deflection of the tip of the wing. The linear theory is found to be conservative with respect to the nonlinear theory for high aspect ratio wings. The findings from this research provide evidence that for more realistic calculation of divergence instability of high aspect ratio wings, geometric nonlinearity should be taken into consideration. This thesis recommends a comparison of solutions for different types of wing models in order to better understand the accuracy of each method.