Drag of Cylinders of Simple Shapes Page: 3 of 8
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DRAG OF CYLINDERS OF SIMPLE SHAPES
sum of the maximum induced velocity near the surface
of the body and the translational velocity equals the
local speed of sound. The flow change at the critical
speed is called, in accordance with earlier terminology,
the "compressibility burble."
The values of the critical speed indicated by the drag
curves for the bodies investigated are less definite than
the values indicated by drag curves for finely shaped
bodies, such as airfoils, because the rise in drag at
high speeds is not very sharp. For the circular cylinder,
however, visual observations of the flow by means of
the schlieren method were made, and these observa-
tions served as a guide in the selection of the value of
the critical speed from the drag curves for the circular
cylinders.
Circular cylinder.-The results from the tests of the
drag of circular cylinders are presented in figures 2
and 3; the results as affected by Reynolds Number2.0
C
t6-
K~ /2 Z
qj
0
U0
d0
t)1132 x
14 +
.1 .2 .3 .4 .5 .6 .7
V/Va
FIGURE 2.-Variation in Cao with V V, for the circular cylinders.FIGURE 4.-Variation in CD with V/V. for the semitubular cylinder.
FIGURE 5.-VarI
(fig. 3) are in good agreement with Relf's results (refer- tion for the
ence 2). cal Reync
S esesber (reference 1 9
SRe'r
Further, these tests indicate that the critical speed is For speed
investigated. The critical speed for the circular function of
cylinder at values of the Reynolds Numbers above the V/ 1. Th
critical probably differs somewhat from that given inasmuch a
herein because of the change in the pressure distribu- range corrReyno/ds Number
ation in C0, with Reynolds Number for the semitubular cylinder.
e circular cylinder that occurs after the criti-
)lds Number is exceeded. The present
results, however, indicate
-Y oometer -- that the critical speed
/i. is unaffected by Rey-
1/16 o nolds Number for ranges
/8 - wherein no marked
changes in the flow
pattern occur. Unfor-
tunately, these tests could
not be extended to higher
values of the Reynolds
Number because tests
of larger cylinders indi-
2 4 6 8/Q6 cated serious tunnel-
wall effects that could
not readily be evaluated.
ids higher than the critical, the test results
d 3) indicate the drag coefficient to be a
f the speed ratio, or compressibility index,
is statement is not a general conclusion
is figure 3 shows that the Reynolds Number
responding to this speed range occurs within171
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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/m1/3/: accessed April 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.