Environmental Engineering Reference
In-Depth Information
Figure 11.4 SUV with covered trailer used in coast down testing
Table 11.3 Trailer specifications
System
Unit
Value
Trailer style: covered
W
m
1.52
H
m
1.87
L
m
2.58
m
2
A
ft
2.56
Mass
kg
~182 (empty)
Tyres ST 205/75 R15
Trailer tongue length
m
1.22
of the SUV and the front face of the trailer is too large to sustain smooth air move-
ment streamlines. As a consequence the drag is significantly higher than if much
tighter spacing, or cowling, could have been used as is done in passenger trains.
This is a very common utility trailer style used in North America and other
countries for transporting camping, sporting equipment and motor sports vehicles.
When the values listed in Table 11.4 are substituted into (11.9) and (11.10), the
results for coefficient of aerodynamic drag and static rolling resistance become
●
C
d
¼
0.874
●
R
0
¼
0.014
The SUV with trailer in tow values are not really surprising. The trailer is not
loaded, so its impact on rolling resistance is negligible. However, the somewhat
larger frontal area of the trailer and the fact that significant space is present between
the SUV and trailer means that drag coefficient will increase significantly. It is
