Catia V5
from Dassault Systemes in Woodlands
Hills, Calif. is the 3D CAD,
and Gillett uses CFD solvers from
several different programs.
“Catia includes a lot of backand-
forth translators, so it communicates
efficiently with downstream
programs,” says Woodward.
“When it comes time to mesh the
CAD model, we use software that
directly imports Catia files so there
is no need to use a third-party file
format. This helps streamline our
workflow.”
The shop focuses mostly on external
aerodynamics. “For example,
we often compare different body
configurations for underbody flow,”
says Woodward. “We select the best
solution from CFD and import the
mesh file for that model back into
Catia. The model is regenerated
from the mesh file to facilitate the
design change.”
Typically, the firm scans a whole
car, imports the point cloud into
Catia, and then builds a model directly
from the point data. “Our
models tend to be large. The number
of cells in a mesh is one way
to measure size of a CFD model.
Obviously, the more cells, the more
accurate the solution. But the limiting
factor is hardware. Right now, we can run maybe 50 million cells.
With hardware continually getting
cheaper, we think we will solve
models 10 times that size in the
next two or three years.”
Expectations are that CFD will
replace the traditional wind tunnel.
“Besides flow, the software optimizes
car components for drag,
downforce, lift-to-drag ratio, side
force, and aerodynamic loads and
moments,” Woodward says. “Because
CFD shows how air moves
around a race car, it allows better
design for specific purposes. For
example, it’s important to reduce
drag for a superspeedway car. But
for a short-track car, it makes more
sense to optimize cooling in the
grille and brakes.”
The Car of Tomorrow spec that
NASCAR is moving to next year
tightly regulates race-car bodies.
“So a lot of underbody flow will
need to be studied,” says Woodward.
“And where previous cars had
a spoiler, the new car has a wing,
one of many variables to investigate.
But studying them must be done in
an intelligent manner. That’s where
the experience of team engineers,
aerodynamicists, and guys building
the cars come in.”