Destabilizing effect of damping on the post-critical flutter oscillations of flat plates

In the framework of energy harvesting from flow-induced vibrations, understanding the behaviour of dynamic systems under high levels of damping is a key issue. In particular, this work refers to two-degree-of-freedom elongated rectangular plates prone to the aeroelastic instability of classical flutter. The effect of heaving damping was studied through systematic linear analyses and wind tunnel tests, developing specific aeroelastic setups for both large-amplitude motion and high viscous forces. Some configurations clearly showed a destabilizing effect of damping, both in terms of earlier instability onset and larger post-critical motion amplitudes. For high-inertia systems with low pitching damping, still-air frequency ratios of the uncoupled system away from unity and small mass unbalance downstream of the elastic axis are the key parameters to observe this phenomenon. Both analytical and experimental results suggest that this destabilizing effect relates to the tendency of any configuration to approach the behaviour of the system with unit still-air uncoupled frequency ratio while increasing the heaving damping