Flow-induced instabilities of a flexibly-mounted rigid plate placed in water*

Flow-induced instabilities of a flat rigid plate placed in water with either one degree of freedom (torsional) or two degrees of freedom (transverse and torsional) are studied. The onset of dynamic instability for each configuration was pinpointed and the post-critical behavior of the system in both 1 DoF and 2 DoF cases was investigated. For the 1DoF case, for all flow velocities higher than the critical, a periodic motion was observed. The amplitude of oscillations increased with increasing flow. For the 2DoF system, a period-doubling route to chaos was observed. The post-critical periodic oscillations were followed by period-2 and later on period-4 oscillations, which led to chaotic oscillations at higher flow velocities. Flow visualizations showed that for periodic oscillations, one vortex was shed in each cycle, and for period-2 oscillations, two vortices were shed in each cycle.