Forces on elliptic cylinders in uniform air stream Page: 3 of 18
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REPORT No. 289
FORCES ON ELLIPTIC CYLINDER IN UNIFORM AIR STREAM
By A. F. ZAEM, R. H. SMITH, and F. A. LOUDEN
INTRODUCTION
This report presents the results of wind tunnel tests on four elliptic cylinders with various
fineness ratios, conducted in the Navy Aerodynamic Laboratory, Washington. The object of
the tests was to investigate the characteristics of sections suitable for streamline wire which
normally has an elliptic section with a fineness ratio of 4.0; also to learn whether a reduction in
fineness ratio would result in improve-
ment; also to determine the pressure
distribution on the model of fineness
ratio 4.
Four elliptic cylinders with fine-
ness ratios of 2.5, 3.0, 3.5, and 4.0
were made and then tested in the 8
by 8 foot tunnel; first, for cross-wind
force, drag, and yawing moment at
30 miles an hour and various angles
of yaw; next for drag at 00 pitch and
0' yaw and various wind speeds; then
for end effect on the smallest and FG,. .-Elliptic cylinder 2 by 5 inches mounted with end plates
largest models; and lastly for pressure distribution over the surface of the largest model at 0'
pitch and 0' yaw and various wind speeds. In all tests, the length of the model was transverse
to the current. The results are given for standard air density, p=.002378 slug per cubic foot.
This account is a slightly revised form of Report No. 315, prepared for the Bureau of Aero-
nautics, July 13, 1926, and by it submitted for publication to the National Advisory Comnimittee
for Aeronautics. A summary of conclusions is given at the end of the text.
DESCRIPTION OF MODELS
The four elliptic cylinders, the smallest of which is shown in Figure 1, and profiles of which
are shown in Figure 10, were each 62 inches long and 2 inches thick; their widths were 5, 6, 7,
and 8 inches. The specified offsets are given in Table 1 and for each case can be derived from the
equation of an ellipse. All of the cylinders were of laminated pine, varnished, and then verified
by application of their construction templates. After the tests, however, a few measurements of
offsets taken on the plane table indicated that the models were slightly unsymmetrical. The
2 by 8 inch cylinder had detachable end segments to fill up the space between the floor and ceiling
of the tunnel during the pressure distribution test.
In a second test series adjoining end plates, Figure 1, were used to determine the end effect
on two of the cylinders. They were made from fairly plane galvanized-iron plate and measured
24 by 24 inches.
In Figure 2 the pressure collector is shown inserted as a center segment in the 2 by 8 inch
model. It was made of bronze accurate to 0.001 inch in the offsets. Its dimensions and the loca-
tion of its 16 holes are given in Figure 3. The pressure leads, one running from a hole in the nose
and the other successively from each surface hole, were each connected with 1-inch tubing
which ran lengthwise through the strut to a manometer outside the tunnel.
4920--29-15 217
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Zahm, A. F.; Smith, R. H. & Louden, F. A. Forces on elliptic cylinders in uniform air stream, report, 1929; (https://digital.library.unt.edu/ark:/67531/metadc65943/m1/3/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.