Tesla S Aerodynamics

[ERTW]

I came across this and thought it interesting:

From: http://www.sae.org/mags/aei/12384

Engineers primarily used CFD for design, and wind tunnels for validating the Model S sedan.

The result is a full-size electric sedan with a drag coefficient of 0.24.”

http://www.youtube.com/watch?feature...&v=xPSZ52GDLt8

[...]

Tesla used the traditional process of optimizing the overall shape of the vehicle followed by optimizing the individual details.

Front:

[...] Exa consultants did a parametric study of changing the shape of the headlights and the area around the headlights with the goal of turning the air sharply so it adheres closely to the sides of the vehicle.

Wheels:

[...] “The wheels generate up to 20% of the drag on the vehicle so airflow around the front wheels is critical,” Palin said. “One of the objectives with the Model S was to minimize the airflow around the front wheels and to line up the airflow so it hits the front wheels head on. We needed to avoid air hitting at an angle, as often the side of the tire acts like a bucket that catches the air, producing significant drag.

Windshield/A pillars:

[...] Aerodynamicists used parametric analysis to optimize the curvature of the A and C pillars to minimize vortex formation. The side glass inset was minimized and the B pillar was eliminated entirely to further minimize drag.

Progress & validation:

[...] “early design concepts of the Model S was 0.32,” Palin said. “The major shape changes reduced the drag to 0.27, and the smaller changes provided further improvement to 0.24. These numbers were validated with wind tunnel testing "

Full article: http://www.sae.org/mags/aei/12384

[NeilBlanchard]

At one point before they released the final design, they quoted a Cd of 0.22. I'm thinking that the change may have been largely the wheels they ended up with; or the mirrors? Maybe they can introduce some plan taper on the sides and lower it?

[MetroMPG]

Just a note for everyone, FYI: you're welcome to post summaries/excerpts of articles from other sites, but please avoid copy/pasting entire articles.

Best to quote relevant sections, and link to the source. Otherwise we'll get busted on copyright grounds. (Also it's just good web etiquette.)

[SoobieOut]

Bump

Here's a newer article about Tesla S being the most aerodynamic car on the road.

Tesla Model S Wins Wind Tunnel Wars - Business Insider

May get a few arguments there...

[redpoint5]

Amazing that the Tesla didn't do even better. It's just barely more efficiently designed than the Prius, despite having no engine to cool and little to no grill opening.

The Leaf is just pathetic. Aero efficiency is most important on a car that doesn't go very far and takes a long time to "refuel". Plus, with an all electric drive-train, the shape can easily be made efficient since components can be located anywhere and don't generate much heat.

[2000mc]

Originally Posted by redpoint5

Amazing that the Tesla didn't do even better. It's just barely more efficiently designed than the Prius, despite having no engine to cool and little to no grill opening.

The Leaf is just pathetic. Aero efficiency is most important on a car that doesn't go very far and takes a long time to "refuel". Plus, with an all electric drive-train, the shape can easily be made efficient since components can be located anywhere and don't generate much heat.

Thanks redpoint5, I really glossed over this fact. What kind of Cd do you think a prius with a closed off grill, no exhaust, and a flatter underside would get?

[NeilBlanchard]

The Model S is the largest frontal area in the test - and yet it tied for 1st for CdA. It would do better with smooth flat wheels and video side mirrors - which if Tesla can get the regulations changed, I'm sure they will add to the Model S.

[kafer65]

I just watched many of the EXA corperation Utoob videos. They had heat, sound and aero simulations that were very interesting. The Deutz tractor and the small SUV analog captured my attention the most. The SUV was being compared to itself with changes to the front approach and rear taper. Makes me want to attempt front wheel covers even more!

[RunningStrong]

The CLA figure is most likely quoted for a European Eco model (Though I note they quote an official 0.22 for the BlueEfficiency). It's also probably highly sensitive to whatever sports, trim or wheel set is selected.

Originally Posted by redpoint5

The Leaf is just pathetic. Aero efficiency is most important on a car that doesn't go very far and takes a long time to "refuel". Plus, with an all electric drive-train, the shape can easily be made efficient since components can be located anywhere and don't generate much heat.

Probably because the Leaf was designed to be exceptionally practical and more of a city-car than a tourer like the Tesla S?

A low slung saloon is not what older people, and people with children, would consider a practical car. A more upright vehicle with a step-up cabin is a much more usable and practical vehicle.

[NeilBlanchard]

Having a low Cd does not correlate to an impractical car. The Leaf could be improved a lot with affecting it practicality. Case in point is the Prius; it is more practical than the Leaf. The Model S is also and example of a much larger car that has the same drag as the Prius.