Nonlinear aeroelastic analysis of complete aircraft in subsonic flow

Aeroelastic instabilities are among the factors that may constrain the Righ t envelope of aircraft and, thus, must be considered during design. As futu re aircraft designs reduce weight and raise performance levels using direct ional material, thus leading to an increasingly flexible aircraft, there is a need for reliable analysis that models all of the important characterist ics of the fluid-structure interaction problem. Such a model would be used in preliminary design and control synthesis. A theoretical basis has been e stablished for a consistent analysis that takes into account 1) material an isotropy, 2) geometrical nonlinearities of the structure, 3) unsteady Row b ehavior, and 4) dynamic stall for the complete aircraft. Such a formulation for aeroelastic analysis of a complete aircraft in subsonic flow is descri bed. Linear results are presented and validated for the Goland wing (Goland , M., "The Flutter of a Uniform Cantilever Wing" Journal of Applied Mechani cs, Vol. 12, No. 4, 1945, pp. A197-A208). Further results have been obtaine d that highlight the effects of structural and aerodynamic nonlinearities o n the trim solution, flutter speed, and amplitude of limit-cycle oscillatio ns. These results give insight into various nonlinear aeroelastic phenomena of interest: 1) the effect of steady-state lift and accompanying deformati on on the speed at which instabilities occur, 2) the effect on nonlineariti es in limiting the amplitude of oscillations once an instability is encount ered, and 3) the destabilizing effects of nonlinearities for finite disturb ances at stable conditions.