Reduction of transonic buffet onset for a wing with activated elasticity

Abstract

Transonic buffet, a kind of aerodynamic instability at a certain combination of Mach number and angle of attack, limits the aircraft flight envelope and fatigue life. The traditional method on transonic buffet onset prediction has an obvious limitation for an elastic wing, which ignores the feedback of oscillatory structure to the fluid. In this paper, the reduction of transonic buffet onset is observed when the feedback is considered for a wing with an activated pitching degree of freedom; that is, buffet will be provoked at some special structural parameters in pre-buffet flow conditions. This phenomenon is not caused by the static deformation of the structure but the coupling effect between fluid and structure. Besides, the dynamical characteristic and instability mechanism are significantly different from the SDOF (single degree of freedom) flutter [18]. The SDOF flutter is caused by the instability of the structural mode, and the flutter frequency locks into the structural frequency, while the present instability is governed by the fluid mode and the coupling frequency follows the buffet frequency in post-buffet conditions.