Diffuser Stall

**JustBringIt** · 10th February 2006, 02:50

Thinking on it, I don't know that flexing of the diffuser would be allowed because I think the regs say that none of the aerodynamic elements are allowed to flex, and the diffuser should fall into that category.

**SS454** · 10th February 2006, 02:54

Dont they only have a flex test for the front and rear wings?

**JustBringIt** · 10th February 2006, 03:02

Originally posted by SS454
Dont they only have a flex test for the front and rear wings?

Possibly but if they found anyone gaining an advantage from anything else flexing, they would surely test them, too. The wing test has only existed for a couple of years but the rule has been there for much longer.

**fermy** · 10th February 2006, 04:08

But what part would flex. The diffuser ducts get bigger as they go to the back of the car. My guess, is they could make the front of the diffuser ducts more flexible than the rear of the ducts. Which means the front of the ducts would increase in size, and decrease the steepness of the angle of the diffuser duct, decreasing the effectiveness of the diffuser. But I don't think that would cause the stall effect we are looking for. (this could be completely stupid and impossible, its just an attempt to explain the "Flex" theory, which I like.)

If my diffuser flexing theory is indeed true, as speed increases, the angle of some part of diffuser should increase too. Now imagine an upper part of diffuser as rigidly attached at the back (of the car), but not attached at the front. As the speed increases, the air pressure in diffuser will drop, forcing the front (unattached) part to move down, thus increasing the angle of attack.

**SS454** · 10th February 2006, 04:16

I dont think your going to want a moveable gap between the diffuser and the rest of the undertray, that would not be good for downforce or drag. However, the "fences" as coysht called the, could flex when they were angled in like the pic showed in page 1. Or the "endplates" of the central channel, though Im not sure either would benifit the overall diffuser design.

**fermy** · 10th February 2006, 04:26

You can prevent the movable gap with the undertray by making the front lip of diffuser to extend forward beyond the point of juncture with the undertray, thus covering the gap.

**SS454** · 10th February 2006, 04:55

That would be considered as moveable aerodynamics. Though aero pieces can flex, the have to be fixed/stationary.

**coysht** · 10th February 2006, 09:16

Originally posted by JustBringIt
Sorry to rain on your parade, coysht, but a diffuser creates a slower velocity of fluid/air. If you think of it in terms of volumetric flow rate, you see what I mean... Unless I'm wrong.

:

Oh yeah.

As I said in that post - its open to future corrections!

edit:

Hang on, on re-reading my original post, I think what I've got is technically right, but badly writen.

I'll go and edit it so it makes more sense.

**ferrarista** · 10th February 2006, 10:35

AS explains how the concept works, but i didn’t traslate it because I don’t know the exact words in English; now i try to make a small effort.

The undertray of the car gets deformed by the pressure of the air at high speeds (Ferrari works to have it in a predicted way). It stalls and doesn’t produce downforce anymore (useful on the straights because the top speed goes up). The system was efficient on the F2004, but Ferrari had to abandon it in 2005 because of the rule changes.
Ferrari now want to achieve again this through special materials called ‘composite materials with memory of shape’ (roughly translated from ‘materiali con memoria di forma’).
I read one or two years ago that these materials get deformed at certain speeds depending on the pressure and the temperature.
Fia don’t control the undertray of the cars, so they are legal; anyway, those materials are able to go back to the original shape, so let’s say in the pitlane Fia wouldn’t find anything illegal in the case they want to control the undertrays.

AS also writes that at the moment Ferrari is as quick as Honda on the straights; as soon as the concept works properly, they should have an advantage over the rest.
I guess they are testing today important solutions for the problem at Vairano, where according to gazzetta and tuttosport the 248 should have important new parts for its underneath.

**fermy** · 10th February 2006, 10:39

Aha, basically the same deformation idea, but with the undertray.

**S.F. 1** · 10th February 2006, 10:53

I hope the discussion about this isn't getting to big everywhere....the FIA might ban the deformed undertray as well....

**fermy** · 10th February 2006, 11:56

If we win by a blowout they sure will ban it. Otherwise it should be fine.

**Cavallino** · 10th February 2006, 19:47

So the flex theory is correct.

Congratulations

It sounds easy enough, but also sounds too easy for other teams to figure out and use to their advantage.

**fermy** · 10th February 2006, 20:04

Woohooooooooo.

Regarding it being too easy, that's something I was wondering too. Once you know the stall idea, you should be able to figure out the rest. Either Ferrari are just misleading or the real know-how is not the controlled stall per se, but something on top of that.

**ferrarista** · 10th February 2006, 20:13

yes, it's easy in theory.
AS reported in 2004 that Ferrari are masters in the treatment of the materials i mentioned above, those materials are the secret to make the concept work properly.
And it was reported that Tombazis was decisive for this reason when he joined Mclaren, he brought to them years of experience of Ferrari in that sector.

**JustBringIt** · 10th February 2006, 21:40

Originally posted by coysht
:

Oh yeah.

As I said in that post - its open to future corrections!

edit:

Hang on, on re-reading my original post, I think what I've got is technically right, but badly writen.

I'll go and edit it so it makes more sense.

Hmm... I'm not so sure because slower air results in higher pressure, not lower, according to Bernoulli.

**coysht** · 10th February 2006, 22:44

Originally posted by JustBringIt
Hmm... I'm not so sure because slower air results in higher pressure, not lower, according to Bernoulli.

If you re-read the post it says that the slower air is in the diffuser, the faster (lower pressure) is under the car.

**JustBringIt** · 10th February 2006, 22:50

Originally posted by coysht
If you re-read the post it says that the slower air is in the diffuser, the faster (lower pressure) is under the car.

Ok, in that case I'm not understanding something. What do you mean when you say the air is "in" the diffuser?

**coysht** · 10th February 2006, 23:19

Originally posted by JustBringIt
Ok, in that case I'm not understanding something. What do you mean when you say the air is "in" the diffuser?

Air that is neither under the car nor behind it will be in the area of the diffuser. Since the diffuser is a series of 3 sided ducts (top and two sides), its safe to say the air is in the diffuser.

**killer** · 11th February 2006, 05:22

Originally posted by coysht
If you re-read the post it says that the slower air is in the diffuser, the faster (lower pressure) is under the car.

Is the faster air a result of air being slowed down in the diffuser or vice-versa?

**coysht** · 11th February 2006, 09:49

Originally posted by killer
Is the faster air a result of air being slowed down in the diffuser or vice-versa?

the first of those

**19000rpmF-2004** · 15th February 2006, 14:23

this is the Mc diffuser. no to clear but we can see how it is.

**JustBringIt** · 15th February 2006, 21:24

And I'll bet you didn't even change the brightness on that picture, that's just what the chrome looks like in the sunlight.

:

**Tommy_F** · 17th February 2006, 14:34

:)

**SS454** · 4th March 2006, 18:55

I was just reading an old Road and Track magazine from 2000, and there was an article about Ferrari's technology, and one of them was the flexable undertray/diffuser. They talked a little about having movable panels made from carbon fiber, but Ferrari said initial results showed the pieces were too fragile and needed more durable parts. Its interesting to note that back in early 2000, Ferrari were working on these deformable undertray/diffuser for their road cars, which we know take technology from the F1 cars.

**Luca de Montezuma** · 8th March 2006, 06:36

How's this for a diffuser and a half!

**antares** · 2nd April 2006, 21:10

LOL @ Luca de Montezuma

Killer, about the turbulence (yeah I know I'm really late), the air coming out of the diffuser is back at the speed of the air flowing over the car. It's also moving in the same direction as the upwash from the rear wings. If the speeds were indeed not matched, there would be a ton of turbulence, lots of eddies behind the car, and far too much drag to be useful.

**stefano** · 21st April 2006, 09:15

Originally posted by antares
LOL @ Luca de Montezuma

Killer, about the turbulence (yeah I know I'm really late), the air coming out of the diffuser is back at the speed of the air flowing over the car. It's also moving in the same direction as the upwash from the rear wings. If the speeds were indeed not matched, there would be a ton of turbulence, lots of eddies behind the car, and far too much drag to be useful.

Yes, that is my thought too.

Obviously I am no expert on the matter and stand to be corrected, but, following from JBI and coysht's discussion on air under the car / in the diffuser etc., the bottom line is that if the air is not SPED UP underneath the car in the first place, there is no downforce to speak of! So slowing air down that has not been sped up doesn't make much sense.

In that respect, in my mind the main goal of the diffuser is to "clean" the air that comes out from underneath the car and create the least bit of turbulence possible.

Where has my reasoning gone wrong?

:

**coysht** · 21st April 2006, 09:29

Originally posted by antares
LOL @ Luca de Montezuma

Killer, about the turbulence (yeah I know I'm really late), the air coming out of the diffuser is back at the speed of the air flowing over the car. It's also moving in the same direction as the upwash from the rear wings. If the speeds were indeed not matched, there would be a ton of turbulence, lots of eddies behind the car, and far too much drag to be useful.

The air above and exiting from below the car do not have to be going at the same speed to get clean(ish) flow, as almost all aerofoils will have a slight speed differential between the upper and lower surfaces, and the air that is separated at the leading edge does not have to join back up where it left off at the trailing edge.

Now this is where we go off into Tom's best guess land....

I do wonder if the turbulent air from the diffuser isn't fed into the void below the rear wing upwash in such a way that the drag generated is not too large, and the downforce is a much bigger benifit.

This might fit, as the air directly behind a car is quite turbulent, and alot of people in F1 have been saying that the way to improve the air for a following car is to leave the rear wing and cut back the diffuser.

However I could be (very) wrong.