A Note on the Post-Flutter Dynamics of a Rotating Disk

The dynamic response of a thin, flexible disk spinning in an enclosed air-filled chamber, beyond the onset of aeroelastic flutter, is investigated experimentally. The results describe the occurrence of new nonlinear dynamic phenomena in the post-flutter regime. A primary instability leads to the Hopf bifurcation of the flat equilibrium to a finite amplitude backward traveling wave. A secondary instability causes this traveling wave to jump to a large-amplitude frequency locked, traveling wave vibration. For a small range of rotation speeds, both types of traveling wave motions co-exist. The results underscore the interplay between structural and fluidic nonlinearities in controlling the dynamic response of the fluttering disk in the post-flutter regime.