Experimental measurements were made of the unsteady cavity
and force characteristics for both forced and naturally ventilated
hydrofoils of finite span submerged below a free surface. Unsteady
cavity characteristics were studied for a force-ventilated wedge
subjected to a sudden change in either the .air flow rate to the
cavity or angle of attack. Differences were observed in air entrainment
rates measured for the unsteady case as compared to the
corresponding instantaneous steady case. The magnitude of the differences
depended on the kind of unsteadyness introduced.
Unsteady force characteristics were determined for naturally
ventilated foils undergoing either a sinusoidal heaving motion or
a harmonic oscillation of a trailing edge flap. The amplitude of
the oscillatory lift was found to increase with increasing reduced
frequency for a heaving foil, whereas the oscillatory lift was
essentially constant up to reduced frequencies of 1.2 for the foil
with an oscillating flap. There is limited agreement of the data
with available theory.
Wetzel, Joseph M.; Foerster, K. E..
Unsteady Force and Cavity Characteristics for Ventilated Hydrofoils.
St. Anthony Falls Laboratory.
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