BMW tests delta / strake style roof mounted vortex generators

[MetroMPG]

You saw it here first, folks!

While perusing the photos of BMW's new wind tunnel facility, I happened to notice the strakes on the top of a 3-series model being smoke tested on their rolling road:



Oooh!

OK, yes I'm being a bit facetious... people seem to latch on to VG's as a magic bullet, and they're not. Remember: when optimized by Mitsubishi, they estimated delta style VG's made a difference of -.006 to the drag coefficient of the Evolution sedan.

-006 is nothing to sneeze at, don't get me wrong. But it's not a magic bullet, and a change of that magnitude won't show up in either tank-to-tank or controlled-as-possible testing:

• Tested: vortex generators (AirTabs) on a Toyota Corolla
• Tested: Airtabs on a mini van, A-B-A - no measurable effect
• Documenting NHW11 Prius rear window flow separation; testing AirTab vortex generators

I think what's MUCH more significant from BMW's testing is the full set of four fender skirts that automatically cover the 3-series wheel wells after it jettisons the wheels and enters flying mode:

[winkosmosis]

Interesting setup, with the wheels being a part of the facility. What happens if the guy falls onto the treadmill? Looks like precarious footing on that smooth ledge...

[tasdrouille]

This thread is useless without a research paper :P

Cool though. I'd like to see some numbers, but probably half a point at best, highly dependent on chord placement.

[aerohead]

Elegant way to separate aero from combined aero/RR drag.-------- Does the large ground clearance in the second photo confirm rumors of BMW's upcoming Monster-Series?

[Christ]

Originally Posted by winkosmosis

Interesting setup, with the wheels being a part of the facility. What happens if the guy falls onto the treadmill? Looks like precarious footing on that smooth ledge...

Laser Beams, man... Laser beams.

I was actually wondering the same thing... I bet there's a "hey, there's weight in the wrong place!" sensor that shuts it off or something.

[DonR]

Hopefully the dorks turned off the rolling road when the car was up in the air.

Lots of testing on race cars has the wheels not attached to the car. So you can tell the aero load on the wheels & this way you don't have to build scale suspension systems.
The car is rigidly mounted so you can measure the pitching moment generated by the body. The body itself won't pitch though.

I am guessing that they are using the wind tunnel they use for their F1 cars.

Don

[TimJFowler]

Originally Posted by MetroMPG

I think what's MUCH more significant from BMW's testing is the full set of four fender skirts that automatically cover the 3-series wheel wells after it jettisons the wheels and enters flying mode:

Ah Ha! so at least BMW is finally admitting to having flying cars! When do they appear in the showroom?