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 02-27-2013, 06:54 PM #11 (permalink) Aerodynamics rules     Join Date: Feb 2013 Location: Argentina Bs. As. Posts: 63 Thanks: 9 Thanked 1 Time in 1 Post Then... i find the trick yes! :P Also that air is channeled to the rear wing nice... at same time the air there fills the wheel low pressure ... but... i mean, theres a good line at sides of the wheels and rims are created to have low turbulence so i don't think that there's a low pressure on the back of the wheel... so why it should have less drag? maybe the answer is where it starts, maybe the aerobridge divides better the air. and maybe the air that pass for the aerobridge goes slower than the rest, and then maybe it copies more the form of the car, like going to less speed, then less have less drag... It's really channeled to the rear wing? maybe that air just go to sides of the car, if it's like that you'll have less drag, maybe just the air that passes up of the side ''wing'' goes to the rear wing. ... i love you ferrari engineers hahahaha
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Quote:
 Originally Posted by Viturro ........ i don't think that there's a low pressure on the back of the wheel... so why it should have less drag?
The faster moving air just above the wheel will have the tendency to draw higher pressure air to it. It literally sucks up the surrounding air.

Another example: I have a roof wing on my pick up truck. The small gap between the roof and the wing accelerates air downward at a 45 degree angle (I beveled the edge). This air curtain of sorts draws in the higher pressure air above it, allowing my rear spoiler to be more effective as the air moves along the top of the bed cover.

Higher velocity air = low pressure

Lower velocity air = higher pressure

By forcing air though a narrowing opening the air is accelerated, thereby increasing velocity and lowering the air pressure.

The higher pressure surrounding air will rush to fill the void and gets sucked in and follows.
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1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

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

 02-27-2013, 07:37 PM #13 (permalink) Aerodynamics rules     Join Date: Feb 2013 Location: Argentina Bs. As. Posts: 63 Thanks: 9 Thanked 1 Time in 1 Post so...in the back of the car we have high pressure air?? the drag is high pressure air? Last edited by Viturro; 02-27-2013 at 07:54 PM..
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Quote:
 Originally Posted by Viturro so...in the back of the car we have high pressure air?? the drag is high pressure air?
If I'm thinking correctly you are asking about the section of the car/truck body which is typically flat across the rear.

In this case there is no flow of air.

No higher pressure or lower pressure, only a lack of pressure caused by the vehicle body moving though the air.

In part, the rolling vortexes of turbulence at the rear corners, end/top of vehicles are permitted to form because of this lack of pressure.

Had there been pressure back there, air flow could not go crazy and would be forced to conform to a flow, much as it does against the skin of the vehicle body. The body of the vehicle exerts an equal pressure, if it does not, it will flex like fabric does.
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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

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

 02-28-2013, 11:37 AM #15 (permalink) Aerodynamics rules     Join Date: Feb 2013 Location: Argentina Bs. As. Posts: 63 Thanks: 9 Thanked 1 Time in 1 Post ''No higher pressure or lower pressure, only a lack of pressure caused by the vehicle body moving though the air.'' ¿? That lack pressure just can be low pressure air, i mean there is air, and just can be low pressure, (if that were high pressure air the car should have no drag, should have a boost). And we know that there is air, because if there were not it will be a vacuum pump, and if there is vacuum the car couldn't even move even with 4000hp So there is low pressure air. (if I'm wrong let me know why, please). I think that the Venturi effect only happens in tubes (or closed spaces). Wasn't the N.A.S.A. the ones that say that the air planes didn't fly because of Venturi effect, they fly because the wings send the air below it?(short version). Last edited by Viturro; 02-28-2013 at 11:44 AM..
 02-28-2013, 11:45 AM #16 (permalink) Master EcoModder     Join Date: Aug 2012 Location: northwest of normal Posts: 27,852 Thanks: 7,819 Thanked 8,636 Times in 7,114 Posts My favorite example, because it's on a Volkswagen.
 02-28-2013, 11:47 AM #17 (permalink) Aerodynamics rules     Join Date: Feb 2013 Location: Argentina Bs. As. Posts: 63 Thanks: 9 Thanked 1 Time in 1 Post that is the vw golf w12? nice... example of what? hahaha (← ← ← VW lover here ← ← ←)
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Quote:
 Originally Posted by Viturro that is the vw golf w12? nice... example of what? hahaha (← ← ← VW lover here ← ← ←)
I THINK A ROOF WING AND POSSIBLE SIDE CURTAIN/FOILS.

Oops caps were on.

woerthersee07w2.jpg Photo by g60brown | Photobucket

Volkswagen Golf GTI W12 650 Concept | Flickr - Photo Sharing!

Golf GTI W12-650 Concept Revealed - Photos

Got it at last, that last image captures it.

Viturro, the high pressure low pressure thing with velocity phrase is taken from the what makes airplanes fly rule book.
Attached Thumbnails

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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

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

Last edited by kach22i; 02-28-2013 at 02:55 PM..

 02-28-2013, 04:57 PM #19 (permalink) Master EcoModder     Join Date: Aug 2012 Location: northwest of normal Posts: 27,852 Thanks: 7,819 Thanked 8,636 Times in 7,114 Posts Sorry, what kach22i said. It's an external aero duct. Occasionally, someone will concoct a plan to run a duct from the front stagnation point to the back to raise the base pressure, but of course skin friction would kill it so there's nothing to be gained. But, IMHO, a short, large duct can be useful externally. I think the Ferrari is a good example, diverting air sideways before it piles up under the windshield. I don't know if it would do much downstream. The GTI W12-650 is essentially a bubble-top coupe body inside of a hatch-back. That gains plan taper and an integrated wing. It diverts 5-10x more air, and there is no downstream to make claims about. So I think it is a better example.
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Quote:
 Originally Posted by freebeard external aero duct.
Good description/classification.

Quote:
 Originally Posted by freebeard I think the Ferrari is a good example, diverting air sideways before it piles up under the windshield. I don't know if it would do much downstream.
It is taking air from the stream before it gets to the windshield, and to be clear, not from windshield pressure build up. It is more like half of a NACA duct (see image far below)

Quote:
 Originally Posted by freebeard The GTI W12-650 is essentially a bubble-top coupe body inside of a hatch-back.
I had not been aware of this car before today, thank you for posting it.

NACA Duct
NACA Duct - Speedway Motors, America's Oldest Speed Shop

From the first page:

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George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

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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