NON-LINEAR AEROELASTIC BEHAVIOR OF HIGHLY FLEXIBLE HALE WINGS

摘要

High aspect ratio aircrafts, such as High-Altitude Long-Endurance (HALE) UAVs, can experience large static deflections during normal flight operations that could severely reduce the flutter speed. At such speeds, Limit Cycle Oscillations (LCOs) may occur, reducing their operational life. A time-marching solver of a nonlinear aeroelastic model is proposed as a design analysis tool for highly flexible aircraft. Within this nonlinear aeroelastic model, moderate to large structural deflections and linearon linear static and dynamic aeroelastic responses of such flexible aircraft can be properly considered. A geometrically consistent non-linear structural model is adopted based on Hodges and Dowell, including Da Silva second order geometrical non-linear terms. The structural model has been coupled with an unsteady aerodynamic model for an incompressible flow field, based on the Wagner aerodynamic indicial function, in order to obtain a non-linear aeroelastic model. This procedure enables one to expedite the calculation process. The influence of selected design aeroelastic parameters, such as tip deflection and stiffness ratio, is studied. In addition to analytical and computational results, a high aspect-ratio wing model has been selected as a candidate for a feasibility experimental study and to validate the theoretical model. Preliminary results on a balsa wing model and theoretical comparisons are presented.