Non-linear aeroelastic investigations of store(s)-induced limit cycle oscillations

Abstract

In the current work, the study of the aeroelastic behaviour of a wing with external store(s), such as a missile or drop fuel tank, is presented. The aeroelastic governing equations derived for a cantilever wing with coupled bending and torsion modes account for structural and aerodynamic non-linearities. Coupling terms retained in the aeroelastic governing equations are due to: (a) the non-linear beam theory, (b) the aerodynamic non-linearities of a quasi-steady model with stall, and (c) the non-linear kinematics terms of the store(s). As presented in the paper, this aircraft configuration can induce pathologies, such as store(s)-induced limit cycle oscillations (or si-LCOs), very different from the one of a clean wing configuration, and from the one obtained from the linearized form of the aeroelastic governing equations. Time domain simulation, phase portrait, and bifurcation analyses are performed for various velocities, initial conditions, and store(s)-sensitive parameters — such as store mass, number, location along the wing — to examine the dynamic aeroelastic instabilities of the system (e.g. the onset of flutter and LCO). Numerical studies indicate the presence of regions of subcritical Hopf-bifurcation, corresponding to an unstable LCO, for velocities below the linear flutter velocity.