Flutter of circulation control wings

Abstract

The flutter instability of a high aspect ratio circulation control (CC) wing is examined using a lumped-parameter approach in conjunction with a modified unsteady aerodynamic strip analysis method. A low-speed flutter instability unique to wings employing circulation control blowing is identified. This phenomenon, termed is a single-degree-of-freedom bending mode instability. The origin of the instability is the negative lift curve slope that occurs at combinations of moderate angle of attack and high blowing level. The effects of several design parameters on CC flutter are presented, including blowing level, torsion stiffness, bending stiffness, wing sweep angle, and spanwise blowing distribution. Unlike classical flutter, CC flutter depends on wing bending stiffness rather than the ratio of torsion-to-bending stiffness. A relative reduction of outboard blowing is shown to be beneficial for aeroelastic stability of circulation control wings.