Dynamics of an inverted cantilever plate at moderate angle of attack

Kavli Affiliate: Morteza Gharib

| First 5 Authors: Cecilia Huertas-Cerdeira, Andres Goza, John E. Sader, Tim Colonius, Morteza Gharib

| Summary:

The dynamics of a cantilever plate clamped at its trailing edge and placed at
a moderate angle ($alpha leq 30^{circ}$) to a uniform flow are investigated
experimentally and numerically, and a large experimental data set is provided.
The dynamics are shown to differ significantly from the zero-angle-of-attack
case, commonly called the inverted-flag configuration. Four distinct dynamical
regimes arise at finite angles: a small oscillation around a small-deflection
equilibrium (deformed regime), a small-amplitude flapping motion, a
large-amplitude flapping motion and a small oscillation around a
large-deflection equilibrium (deflected regime). The small-amplitude flapping
motion appears gradually as the flow speed is increased and is consistent with
a limit-cycle oscillation caused by the quasi-steady fluid forcing. The
large-amplitude flapping motion is observed to appear at a constant critical
flow speed that is independent of angle of attack. Its characteristics match
those of the large-amplitude vortex-induced vibration present at zero angle of
attack. The flow speed at which the plate enters the deflected regime decreases
linearly as the angle of attack is increased, causing the flapping motion to
disappear for angles of attack greater than $alpha approx 28^{circ}$.
Finally, the effect of aspect ratio on the plate dynamics is considered, with
reduced aspect ratio plates being shown to lack sharp distinctions between
regimes.

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