Sports Utility Vehicles (SUVs) often have blunt rear end geometries for design
and practicality, which is not typically aerodynamic. Drag can be reduced with a
number of passive and active methods, which are generally prioritised at zero
yaw, which is not entirely representative of the “on road” environment. As such,
to combine a visually square geometry (at rest) with optimal drag reductions at
non-zero yaw, an adaptive system that applies vertical side edge tapers
independently is tested statically.
A parametric study has been undertaken in Loughborough University’s Large Wind
Tunnel with the ¼ scale Windsor Model. The aerodynamic effect of implementing
asymmetric side tapering has been assessed for a range of yaw angles (0°, ±2.5°,
±5° and ±10°) on the force and moment coefficients. This adaptive system reduced
drag at every non-zero yaw angle tested, from the simplest geometry (full body
taper without wheels) to the most complex geometry (upper body taper with
wheels) with varying levels of success; providing additional drag reductions
from 3% to 125%. The system also shows potential to beneficially modify the
cross wind stability of the geometry.
