Computational Aeroelastic Analysis of Store-Induced Limit-Cycle Oscillation

Abstract

Limit-cycle oscillation was simulated for a rectangular wing referred to as the Goland + wing. It was found that the aerodynamic nonlinearity responsible for limit-cycle oscillation in the Goland + wing was shock motion and the periodic appearance/disappearance of shocks. The Goland + structural model was such that in the transonic flutter dip region, the primary bending and twisting modes were in phase and coupled to produce a single-degree-of-freedom, torsional flutter mode about a point located ahead of the leading edge of the wing. It was determined that the combination of strong trailing-edge and lambda shocks which periodically appear/disappear, limited the energy flow into the structure. This mechanism quenched the growth of the flutter, resulting in a steady limit-cycle oscillation. Underwing and tip stores were added to the Goland + wing to determine how they affected limit-cycle oscillation. It was found that the aerodynamic forces on the store transferred additional energy into the structure increasing the amplitude of the limit-cycle oscillation. However, it was also found that the underwing store interfered with the airflow on the bottom of the wing, which limited the amplitude of the limit-cycle oscillation.