Store-induced limit cycle oscillations and internal resonances in aeroelastic systems

Several advanced fighter aircraft designs that carry underwing stores have encountered limit cycle oscillations at speeds well below the predicted flutter velocity. Flight tests suggest that the onset of these limit cycle oscillations is related to the type and location of the stores carried. However, no mechanism has been forwarded to conclusively explain the onset of these oscillations. Internal resonance is a dynamical phenomenon due to the nonlinear coupling between modes of motion. The possibility of nonlinear behavior such as internal resonance in a system can be overlooked in analysis, as linearization of the equations of motion often eliminates crucial nonlinear terms. Internal resonance has been shown to be a theoretically possible occurrence in aeroelastic systems. Nonlinear analysis and simulation of a two degree-of-freedom aeroelastic system pursuant to experimental investigation is described herein. It is suggested that even kinematic nonlinearities inherent in the system should be retained for accurate nonlinear results. High levels of damping complicate the analysis of internal resonance in the experimental system. Nonlinear analysis may facilitate the examination of internal resonance or other nonlinear phenomena in a basic aeroelastic system. © 2000 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc.

Store-induced limit cycle oscillations and internal resonances in aeroelastic systems Conference Paper