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SPACE DIVISION C® CHRYSLER ___
CORPORATION

and wind tunnel tests of automobiles. In addition, all automotive trade journals and publi­
cations will be scrutinized for pertinent articles written within the last ten years. SAE
transactions and publications will be searched for pertinent articles covering the past fifteen
year period. A search will also be made in the Central Engineering Library to review any
related work.

An evaluation of the information developed during this search will be made to
insure emphasis is placed on the proper parameters during testing. For example, Refer­
ences 1 and 4 through 8 present gross results from wind tunnel tests. They show that a
box like car has a greater aerodynamic drag than a streamline car or that allowing flow
through the radiator and engine compartment causes greater drag than if the compartment
is closed. However, no data is available to show how the aerodynamic drag of a box like
car (the present design fad) can be reduced through subtle changes which do not significantly
change the car silhouette, or how internal flow, which must be present, can be channeled to
reduce the overall car drag. Thus, the emphasis of the proposed tests will be placed on
developing data on these subtle vehicle changes (i.e., bumper shape, head lamp fairings,
wheel cover shapes, wheel well opening, grill design, etc.).

Furthermore, the information developed during the search should also reveal
the latest testing techniques and simulation parameters. Recent studies, Reference 5, for
example, have shown that simulating wheel spin on a 3/8 scale model has little or no effect
on the aerodynamic characteristics. Therefore, there appears to be no need to simulate
this particular parameter and disregarding it will result in simpler and less costly models.
Other similai’ parameters can be expected to develop during the study.

Secondly, a study will be made as to the feasibility and economics of full scale
wind tunnel testing, as opposed to scale model testing. Of importance here will also be the
quality of the data. Since small, subtle changes will be made on the model, Reynolds number
(Rn) will be of prime concern. There is some evidence, Reference 5, that R^ has no effect,
at least on the complete configuration. However, for the subtle changes to be made during
the proposed tests this a priori should not be assumed. In aerodynamic model testing, there
are three force ratios which must be considered in order to simulate full scale testing.
These are: Reynolds number, Mach number, and Froude number. Mathematically they are
expressed as

Inertia force VI
~ Viscous force

Inertia force V
mn
Elastic force p
Inertia force
2 Gravity force

5