Flow-induced oscillations of low-aspect-ratio flexible plates With various tip geometries

The distinctive oscillations and induced wake of wall-mounted thin plates with flat, elliptic, and aristate tips were experimentally studied under nearly uniform flows for various Cauchy numbers, Ca. Particle tracking velocimetry and planar particle image velocimetry were used to characterize the dynamics of the plates and surrounding flow. The results show that the oscillations of the plates were dominated by their natural frequency across Ca. The structures underwent distinctive reconfigurations which led to asymmetric distributions of the tip fluctuations with respect to the equilibrium position. Interestingly, the oscillation intensity of the plates reached a local maximum at a critical Cauchy number Ca-cri, which increased with narrower tip. This is explained with a basic model that accounts for the nonlinear structure bending and the flow fluctuations in the vicinity of the structures. The very near wake was characterized by two recirculation regions at sufficiently low Ca, one at the base of the plates and another right above it extending up to the tip. However, the recirculation region near the tip eventually vanished under large structure bending at sufficiently high Ca, which led to increased mean shear. Also, the turbulence levels were dominated by the streamwise component of the velocity fluctuations around the tips, where the aristate tip induced the lowest levels. Published by AIP Publishing.