Dynamics of flexible plates and induced flow under Heaviside acceleration heaving

The dynamics of flexible plates under heaving characterized by top-hat acceleration patterns Π(t) and induced flow were experimentally inspected for various Cauchy numbers Ca and fractions of the time under acceleration τ_a with respect to the period of oscillations T. Simultaneous measurements of the plate motion along their span and the surrounding flow were obtained with particle tracking velocimetry (PTV) and particle image velocimetry (PIV). Results show the modulation of Ca and τ_a on the plate dynamics and, in particular, the induced flow. A simple derived formulation based on the damped harmonic oscillator model effectively predicts the velocity difference between the bottom and top tips of the plates. In general, the plate dynamics and flow exhibited three distinctive patterns characterized by flapping-like motions, intermediate state, and translation-like motions. The occurrence of such patterns depended on the relative instant at the reverse direction within the forced Π(t)-heaving; two of them depending on the sign of u and the other when Δu-> 0, i.e., in the limit of pure translation.