By-pass transition to airfoil flutter by transient growth due to gust impulse

Abstract : We present an experimental study which shows that the mechanism known as transient growth of energy, can cause flutter instability of a nonlinearly flexible airfoil at a wind velocity below the linear critical flutter velocity. A flap mounted upstream a flexible airfoil in a wind tunnel generates a single gust which triggers the plunge and pitch oscillations. This gust is characterized using two-component hot-wire anemometry. For the first time experimental evidence is provided to confirm the theoretical scenario of a by-pass transition to flutter by transient growth. From an engineering point of view, transient growth might explain also the premature structural fatigue encountered in structures subject to wind. © 2009 Elsevier Ltd. All rights reserved.