Drag of Cylinders of Simple Shapes Page: 5 of 8
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DRAG OF CYLINDERS OF SIMPLE SHAPES
fineness ratio to the 2:1 ellipse, however, the change
becomes pronounced.
The results of Wieselberger's tests of circular cylin-
ders of infinite aspect ratio (reference 1) are included
in figure 7. A comparison of these results (considered
as data for an elliptical cross section having a fineness
ratio of 1:1 and obtained under conditions of turbu-
lence either equal to or greater than the low turbulence
of the 11-inch high-speed tunnel) and the results of the
present investigation of the elliptical cross section
having a fineness ratio of 2:1 indicates a decrease in
critical Reynolds Number with increase in fineness
ratio.
2 a
2.4
10
K I I I
- j Wid/h Ang/e of a/tack
, -of face.j , deg I
o i 0in.' /5 45 -
I/8 I -O
14 x + nLL_
O ./ .Z .3 .4 .5 .6 .7 .6
FIGURE 9.-Variation in Cn, with V/V for the square cylinders.
_.8 Ver ,co/ lne
intersects curve
ot tt Length Angle of oattock,
, _ J - - _ of face, t , odeg.
in. QO li45
o 4
/0 z 3 4367 8 i7 10' 2 3 4 5 6 78 /0s
Reynolds Number
FIGURE 10.-Variation in CDo with Reynolds Number for the square cylinders. -
Square cylinder.-The results of the drag testsat the
various angles of attack for the square cylinders are
presented in figures 9 and 10. These results indicate
that the drag coefficient is smaller when a diagonal is
parallel to the wind (a=450) than when the face of the
model is normal to the wind (a=00). The total drag
of models of the same size, however, is smaller at
a=00 than at a= 450.Figure 10 indicates that there is but little Reynolds
Number effect on the drag coefficient of the modelswith a diagonal parallel to the wind. Inasmuch as
the flow probably separates at the sharp edges for all
values of the Reynolds Number, the pressure drag
coefficient tends to remain constant and is such a
large part of the total drag coefficient that the effect
of Reynolds Number is relatively small.
For the square cylinders, face normal to the wind
(a=O0 in fig. 10), at the higher values of Reynolds
Number, the drag coefficient is practically constant
and approximates that of a flat plate set normal to the
wind. At the lower values of the Reynolds Number,
however, the drag coefficient appears to decrease with
decreasing Reynolds Number; incomplete separation
at the forward edges possibly causes this change.0 --45676 /4 5 3 5104 4 676105
Reynolds Number
FIGUoRE 12.-Variation in CD, with Reynolds Number for the triangular cylinders.
Within the Reynolds Number range investigated,
no sudden changes in flow were indicated by the results
of the tests at any of the angles of attack.
The compressibility effects for models with a diag-
onal parallel to the wind (a=450 in figs. 9 and 10)
appear to be independent of Reynolds Number within
the range investigated. This result is in general agree-
ment with the results of the tests of circular cylinders.
Triangular cylinder.-The effect of the apex angle on
the drag coefficient of triangular (isosceles) cylinders is173
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Lindsey, W. F. Drag of Cylinders of Simple Shapes, report, October 27, 1937; (https://digital.library.unt.edu/ark:/67531/metadc66277/m1/5/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.