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Aerodynamic Testing of Scaled Truck Models: Drag Correction Potential Under Yawned Conditions and the Importance of Aerodynamic and Geometric Similarity
Technical Paper
92A133
Sector:
Event:
3rd International Conference Innovation and Reliability in Automotive Design and Testing (1992)
Language:
English
Abstract
This study demonstrated that a modified pressure-signature
method resulted in correlating the wind-averaged drag coefficient
data of a half-scale detailed model and an actual full-scale
vehicle within a 1% to 2% margin for the 7 mph wind speed and 55
mph road speed (7 and 55 mph) and 7 and 30 mph conditions,
respectively.
The half-scale model, representing a 2.2% frontal-area blockage,
was independent of reynolds number effects inside the range of 2.2
x 106 to 4.4 x 106. Cooling airflow was found to be the source
of 3.8% of the total wind-averaged drag coefficient at a reynolds
number of 2.2 x 106, of which the ram and fan airflow
contributions were 66% and 34% respectively. The difference in the
wind-averaged drag due to model form and detail was inversely
proportional to body length: a minimum 2.8% for the full-length
model and up to 11% for a 38% shortened model. Increasing trailer
body length increased drag significantly.