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Courtesy of Valeo Systèmes d'Essuyage
As a Tier 1 supplier to all automotive manufacturers, Valeo Wiper Systems
(VWS) is dedicated to delivering the best product to their customers in
a timely manner. This means that they must continually improve their development
process, improve and validate their virtual design process, and keep their
costs down, all while maintaining or improving product quality. To help
them meet these goals, they have used Fluent software since 1997.
One area where CFD has been applied is a program to minimize the uplift
of wiper blades on cars traveling at high speeds. Historically Valeo engineers
have relied on experimental prototypes to bring about performance improvements
in their products, but increased time demands on the delivery of new products
to their customers have made alternative testing methods necessary. For
this reason, they have turned to CFD analysis as a primary component of
their design process.
Pressure distribution on a typical BTM 550 wiper blade
In 1997 Valeo's BTM 550 "Wiper-Blade on Flat Glass" benchmark
aerodynamic test took 28 days from CAD to grid to CFD analysis. Today,
they have pared this down to a four day development process, an 85% reduction
in design time. VWS engineers use CATIA for geometry creation, and GAMBIT
and TGrid for producing hybrid meshes of approximately 600,000 cells each.
Care is taken in the creation of the boundary layer mesh so that y+ values
fall within the optimum range. During the CFD simulation in FLUENT they
track physical features such as the forces on each wiper element and velocity
and pressure values at various locations in the domain. Through their
work, the engineers have learned that specially designed spoilers on the
upstream side of wind-shield wiper blades can help generate extra downforce
for the blades on the windshield with a limited drag penalty.These spoilers
are now becoming standard additions to wiper blades, resulting in enhanced
wiper performance, especially at high speeds.
Flow path lines and surface velocity vectors behind a wiper blade
Today, Valeo Wiper Systems has a validated CFD design process for windshield
wiper development. Their CFD models yield numerical predictions for a
range of wiper-blade configurations with error margins within 3-4% for
both lift and drag components. An increasing number of VWS projects now
have an integrated CFD design component. One of these new projects is
focusing on eddy patterns behind the rubber blade of the wipers. Another
is examining the movement of blades over specific automotive windshields
during a typical wiper stroke.
Typical wiper hybrid mesh generated in GAMBIT/TGrid
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