Experiments on Transonic Flutter of a Two-Dimensional Supercritical Wing with Emphasis on the Non-Linear Effects.

Kurzfassung

Flutter measurements were performed with a supercritical 2-dimensional wing (section: NLR 7301) primarily in the transonic flow regime. The rigid wing model was mounted in a symmetrical suspension system permitting two degree-of-freedom oscillations in heave and pitch. The motion of the wing was measured non-intrusively by optical methods and steady/unsteady forces are obtained by a piezo-electric balance. A non-intrusive flutter control system was applied based on a laser vibrometer and electrodynamic exciters. It permitted positive and negative feedback. The flutter tests were performed in the Mach number range 0.5<Ma<0.81 and the stagnation pressure range 0.38<p0< 1.2 bar. The transonic dip was found to be a very sharp one at Ma&#610.77. The dynamic pressure for flutter at this minimum is roughly half of the subsonic value (Ma &#61approx 0.5).