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By Philip Postle, Advantage CFD, Brackley, UK
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CAD model of the Ferrari 550 Maranello; the bodywork was obtained using
laser scanning
After changes in the GTS rules for the
2003 Le Mans 24-hour race, Veloqx
Prodrive Racing was faced with reduced
engine power. The rule changes, combined
with the increased competition for this year’s
race, sent the team in search of improvements
in aerodynamic performance, primarily in the
form of drag reduction for their Ferrari 550
GTS Maranello.
To maximize the chances of successfully
improving the car’s performance in a short
amount of time, Prodrive turned to their technical
partners, Advantage CFD. Set up in 1997
by Reynard Motorsport Ltd., Advantage CFD
provides consultancy services to clients in a wide
range of industries.
The Le Mans design project focused on producing a modified rear wing
for the Maranello. While it was known that the onset flow is severely
affected by the presence of the car upstream, there was limited CAD data
for the car’s shell. To overcome this limitation, Advantage CFD
contacted 3D Scanners (UK) Ltd., makers of high-definition, non-contact
laser scanning, reverse engineering, and inspection systems. Prodrive
assembled the required panels at their Banbury headquarters, and 3D Scanners
scanned one side of the car. The point cloud for each body panel was then
placed onto the car coordinate axes using the available CAD data provided
by Prodrive. Once the point clouds were aligned, 3D Scanners passed the
files to Raindrop Geomagic Inc., producers of the Geomagic software package
that converts scan data to highly-accurate polygon and NURBS surface models.
Raindrop Geomagic took eight scans of the Ferrari, wrapped the point clouds,
created a polygon mesh, and automatically generated an exact IGES surface.
The IGES files were then sent to Advantage CFD, where they were imported
into a CAD assembly with the rest of the CAD data supplied by Prodrive.
3D Scanners staff member scanning the Ferrari 550
Pathlines showing the wingtip vortex in the CFD model of the new rear
wing
During the next two weeks, a CFD model was
generated and approximately a dozen different
wing modifications were analyzed at the same
speed as the track tests. Variation in the local
angle of attack on the wing section across the
span of the wing is referred to as the twist distribution.
This distribution was tuned to account
for the variation in the flow angle due to the
presence of the car, so that the local sections were
working efficiently across the entire width of
the wing. The size and scale of the local sections
were then modified so that a classical elliptical
spanwise lift distribution could be achieved. This
type of spanwise distribution reduces the loading
at the tips and hence the strength of the tip
vortex and induced drag produced by the wing.
Standard postprocessing of the first few design
iterations highlighted regions of flow separation
induced by the original mounts, so the wing
mounting system was redesigned to address this
issue. These changes resulted in additional
improvements to the wing.
The models of the original and new wings
were run at yaw conditions to assess the impact
on performance. While both wings suffered similar
reductions in performance, the new wing
nevertheless showed a performance gain over
its original counterpart. Once the final design
had been selected, the CAD model was delivered
to Protoform Patterns, who used CNC (computer
numerical control) machines to produce
the tooling blocks required for production. These
patterns were then used by Prodrive to produce
the new rear wing in time for the track test that
occurred six weeks after the project began. The
results were encouraging: the new wing produced
the same downforce as the original, and
reduced the overall drag by 2.5%.
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