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• January 31, 2017 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Hydrodynamic Characteristics Over a Range of Speeds up to 80 Feet Per Second of a Rectangular Modified Plate Having an Aspect Ratio of 0.25 and Operating at Several Depths of Submersion

An investigation has been conducted to determine the hydrodynamic
characteristics over an extended range of speeds (up to 80 feet per
second) of a rectangular modified flat plate having an aspect ratio of
0.25 mounted on a single strut and operating at several depths of sub-
mersion. Comparisons have been made between these data and data pre-
viously obtained over a lower speed range on a similar flat plate having
an aspect ratio of 0.25 and having the same plan—form shape and area but
one—half the thickness. These comparisons indicated that, in the
absence of cavitation, no significant changes existed at the higher
speeds investigated; The trends shown in the previous low—speed tests
continued to apply.

At high speeds and high.angles of attack for depths of submersion
of a quarter-chord or more, cavitation at the leading edge grew strong
enough to cause a greater decrease in lift coefficient with increasing
speed than would be indicated by the results of the previous investiga—
tions and the present investigation at the lower angles of attack.

Over the lower speed range covered.by the previous investigations
and at a given angle of attack, the lift coefficient was slightly lower
for the thick model used.in the present investigation than for the thin
model previously tested.

The results of hydrodynamic investigations of three rectangular
flat plates having aspect ratios of 1.00, 0.25, and 0.125 and operating
near a free water surface are reported in reference 1. The tares and
interferences between the strut used in these investigations and the
aspect-ratio—O.25 flat plate are reported in reference 2. Because the
load capacity of the balanCe used in these investigations was rather
limited, it was the factor which determined the speed range. As a
result, the range of speeds investigated for the higher angles of attack
was reduced to well'below the maximum speed of the Langley tank no. 2
towing carriage. The present investigation was undertaken in order to
extend the range of speeds to the highest possible towing-carriage speed
at which force and moment—measurements could be taken for the range of
angles of attack up to 20° and in order to investigate more fully the
effects Of cavitation.