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Some Considerations of
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Automobile Lift and Drag
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losses and
Estimate air drag on your automobile by analyzing
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the shape of the vehicle. Reduce it by providing
smooth contours Q □ . Q undersurfaces. cross sectic
found that
thing to ins
to the exac
Joseph J. Cornish III, Aerophysics Dept.
Mississippi State University or so close
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Progress has been made in reducing drag of an lower serai
Iutomobile in motion to values of less than 1/2 production
hose of automobiles of 30 to 40 yr ago. the industr
alloy, and s
range of ter’TTINC
Techniques for drag reduction have not re­
temper onlwer-bea
ceived widespread application and many mod­
zer-bea
ern cars are designed with little heed to aero­
mditioi
dynamic drag reduction. Probably this
circumstance results from the rapid and more
widely accepted improvements in automobile
power plants. Automotive aerodynamics has
been restricted to specific problems such as Free Blw
aerodynamic noise, ventilation and cooling,
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despite the fact that a great potential for drag
blueprints \
reduction is possible.
them to det,
The possibility of ignoring aerodynamic
with USS S
drag by the use of powerful engines has in turn
of course). I
created a new problem, which was of little con­
nearest USS
cern when the speeds now attainable were not
Product Des
possible. The aerodynamic lift generated by
below on th
many modern automobiles is so great that sig­
USS is a reg'
nificant loss of stability and control is felt at
high speeds. This problem, which cannot be r
solved readily by the use of additional power, United States
demands that closer attention he paid to aero­ 525 William P1
dynamic design. The automobile lift problem | Gentlemen:
is complicated because the automobile oper­ I Enclosed is'
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ates at the interface between a solid and a fluid;
I Shaped Stef
therefore, much of the aerodynamic technol­ I Please send1
ogy developed for free bodies is not directly I
I
applicable to the automobile. Name_______ '
I a
I Ti tl e_________t
Automobile Drag I Company
Experimental investigations conducted to de­
Address :
termine the optimum shapes for minimum City .
drag bodies show that a body of revolution I
approximately 2.5 times as long as its diam­
eter produces the minimum drag obtainable
at present speeds and vehicle sizes. The drag
of longer bodies increases because of the in­
creased wetted area, and the drag of shorter
bodies increases as a result of greater pressure
drag caused by flow separation. The drag co­
efficient, CD, of this optimum shape, based Circle Service No. 119
(Continued on next page)
’ARCH 31. 1965
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