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Old 02-29-2012, 01:49 AM   #1 (permalink)
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Spoiler of Vortex Generators (Mazda RX-8)

I was leaving work today and saw a Mazda with an interesting addition on the trunk. It was in Westminster, CA so I'm guessing it was a rice racer hehe. VGs are only supposed to help when on the top of the car and there is a real spoiler, so would this setup have any beneficial effect?



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Old 02-29-2012, 08:48 AM   #2 (permalink)
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Old 02-29-2012, 09:51 AM   #3 (permalink)
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I think the idea of vortex generators is that as the swirling cone of air expands, it matches the contour of the rear window glass, so more air actually stays attached to the car.

Vortex generators glued halfway down the bootlid would do little to nothing, except maybe increase the drag a little bit. I don't think they would have been CFD tested so they are just expensive coathangers for now.
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Old 02-29-2012, 10:13 AM   #4 (permalink)
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Yeah, they don't need a spoiler in order to be functional, but they also do maximize the effectiveness of spoilers. Maybe you should leave him a friendly not about migrating them to the back of the roof?
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Old 02-29-2012, 03:32 PM   #5 (permalink)
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Not only are they on the wrong part of the car, they don't even go with the air flow direction.

See image far below.
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1977 Porsche 911s Targa
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Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
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Old 02-29-2012, 04:50 PM   #6 (permalink)
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Mitsu's rationale. http://www.mitsubishi-motors.com/cor...004/16E_03.pdf
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Old 02-29-2012, 05:53 PM   #7 (permalink)
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VGs

In the photo-albums is an article about VGs that an aeronautical engineer came up with to help flow re-attachment on notchback cars with steep backlights.The car in the article is a Honda Accord.
On aircraft without suction slots or blown wings,VGs can be placed near the wing gap to help the flow re-attach onto a lowered flap at very high angle of attack during landings to prevent stalling.
Hucho tells that on an automotive trailing edge,with no downstream surface for which flow might re-attach,that the benefit of VGs found under 2-dimensional flow flight conditions cannot be duplicated under 3-D flow of bluff bodies in ground proximity.
Which is a polite way to say,forget about them.
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Old 03-02-2012, 12:56 AM   #8 (permalink)
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And thats what I thought haha
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Old 03-02-2012, 01:19 AM   #9 (permalink)
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Even if it is possible to reattatch flow to a bluff surface, why would you want that?

The volt's sharp creases certainly show what chevy's engineers think of that idea.
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Old 03-02-2012, 05:36 PM   #10 (permalink)
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why

Quote:
Originally Posted by wheel_of_steel View Post
Even if it is possible to reattatch flow to a bluff surface, why would you want that?

The volt's sharp creases certainly show what chevy's engineers think of that idea.
When its done with suction,each streamline filament is drawn in towards the center of the vehicle,providing 'camber' if you will to the flow field which helps inject energy into the wake,which would otherwise be full-blown turbulence.
Having that transverse force vector really cuts drag.
But I've only seen it done with a pump supplying the suction.And so far,the pump absorbs more energy than is saved with the suction.
It's a second law of thermodynamics entropy thing.

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