Mclaren Mercedes MP4-25

[Richard]

What reason would they use a snorkel like that and not a simple NACA duct?

to get more air, the question is whatfor? someone suggested that it could lead to the diffuser. don't think that will be the case, but it can't be just driver cooling.

Diffuser?? The idea is to remove air from under the floor, not add to it.

[RDJEHV]

I assume the idea would be to 'drive' the diffuser. speed up the air by injecting high velocity air. Again, I don't think that would be the case.

[horse]

i'm really confused with all this suction stuff etc. with the rear wing

please can some1 explain it simply for me what the theory is?

Thanks and sorry for sounding dumb

Not dumb, perfectly valid question.

So, a wing has, in general, a long curved upper surface and a shorter lower surface (you also get symmetric profiles that are the same top and bottom, but don't worry about that for the mo).

Essentially, packets of fluid that are in contact at the front or leading edge of the wing will be in contact at the back or trailing edge. For this to happen, the flow over the top must travel faster than the flow over the bottom as the top surface is longer.

EDIT: It has been pointed out to me by a later poster that this is in fact the "equal transit-time fallacy". The fluid packets need not meet again at the end of the wing, and most likely won't. In reality, a phenomenon known as circulation is set up about a wing which causes the differential in velocity top and bottom. Lift via circulation can be witnessed when you kick a football and it swerves, for instance. On a wing, the circulation is set up by the shape and angle of attack of the aerofoil and then maintained by the necessity for equal pressure at the sharp trailing edge of the aerofoil. If you removed the external flow from a lifting aerofoil you would see that the remaining velocity travels in clockwise circles about the foil (if the oncoming flow is left to right). Still, personally, I quite like the "equal transit-time fallacy" as a pointer towards circulation theory.

This difference in speed generates a low pressure on the top (suction side) and a high pressure on the bottom (pressure side). This difference in pressure causes the wing to generate lift. Reverse it for a F1 car and you get DF.

Now, the steeper the angle you place your wing relative to the oncoming flow, the higher your lift will be (and drag normally), until at a certain angle the flow attached to the suction side of the wing can no longer hold on and separates. This process simply produces more drag for no extra lift.

If high velocity flow can be injected into the flow on the suction side in the direction tangent to it, then this separation can be delayed with excellent lift benefits (a bit like having an extra wing).

What is odd is that (as far as I can tell) all blown flaps are normally driven by a pump (normally an aircraft engine), yet these F1 versions would be seem to be passive. This is what concerns me about sharing the engine snorkel as the deficit for using the flow from there to blow the slot is likely to manifest itself here as some sort of back pressure. I should imagine it's quite a delicate system which is maybe why the slot size has changed.

Anyway, that's my ten pence worth. Hope that explains the semantics a little better.

[astracrazy]

thanks i understand it a little bit better now!

[BreezyRacer]

One has to wonder .. how much more charged is the airflow at the snorkel inlet than at the rear upper wing surface? On the face of it it seems that when you factor in the drag from the port leading to the rear wing it would be, at best, a wash. I guess we'll all see ..

[RDJEHV]

i'm really confused with all this suction stuff etc. with the rear wing

please can some1 explain it simply for me what the theory is?

Thanks and sorry for sounding dumb

Not dumb, perfectly valid question.

So, a wing has, in general, a long curved upper surface and a shorter lower surface (you also get symmetric profiles that are the same top and bottom, but don't worry about that for the mo).

Essentially, packets of fluid that are in contact at the front or leading edge of the wing will be in contact at the back or trailing edge. For this to happen, the flow over the top must travel faster than the flow over the bottom as the top surface is longer.

This difference in speed generates a low pressure on the top (suction side) and a high pressure on the bottom (pressure side). This difference in pressure causes the wing to generate lift. Reverse it for a F1 car and you get DF.

Now, the steeper the angle you place your wing relative to the oncoming flow, the higher your lift will be (and drag normally), until at a certain angle the flow attached to the suction side of the wing can no longer hold on and separates. This process simply produces more drag for no extra lift.

If high velocity flow can be injected into the flow on the suction side in the direction tangent to it, then this separation can be delayed with excellent lift benefits (a bit like having an extra wing).

What is odd is that (as far as I can tell) all blown flaps are normally driven by a pump (normally an aircraft engine), yet these F1 versions would be seem to be passive. This is what concerns me about sharing the engine snorkel as the deficit for using the flow from there to blow the slot is likely to manifest itself here as some sort of back pressure. I should imagine it's quite a delicate system which is maybe why the slot size has changed.

Anyway, that's my ten pence worth. Hope that explains the semantics a little better.

EDIT: (for grammar)

Maybe you should add that you explain it for an airplane wing instead of f1.

by adding a slot in the wing the flow can be guided better and it attaches longer to the wing. In f1 there is a rule it can only exist of two elements now (so 1 slot), but by using this trick mclaren uses 3 (2slots). look at this drawing: http://centennialofflight.gov/essay/The ... TH17G2.htm

[Pup]

What a great pair of photos...

I do think that the first pic is a before. Even at pit lane speeds, there'd be enough airflow to move some of the flo-viz around like we see here.

But the second shot is fantastic. I'm struck by how evenly the flow-viz is distributed, compared to the images we saw this time last year.

[TheMinister]

What is odd is that (as far as I can tell) all blown flaps are normally driven by a pump (normally an aircraft engine), yet these F1 versions would be seem to be passive. This is what concerns me about sharing the engine snorkel as the deficit for using the flow from there to blow the slot is likely to manifest itself here as some sort of back pressure.

Wouldn't blowing too much air through result in a loss of downforce (if you're not yet approaching delamination speeds on the rear side of the wing)?

So making it a passive system not only simplifies it, it means that air only gets blown through at high speeds- when you dowant it.

A pump blown system would probably incur a major weight penalty, and using the enginer exhaust would just mean the volume was related to the revs- rather than the car speed.

It does make me wonder if perhaps they wouldn't be better off with a fat wing- is that banned? (of course it is, everythings banned these days....)

[Pup]

I think in aviation passive systems are far more common than active ones. And in F1 as well - isn't the whole multiple element wing simply another take on the concept, with the lower element supplying a fast-moving sheet of air to the back of the upper one? And McLaren's 'scoop' from last year - isn't this wing just a development of that?

[horse]

Wouldn't blowing too much air through result in a loss of downforce (if you're not yet approaching delamination speeds on the rear side of the wing)?

Hadn't thought of this. You could possibly "over-blow" and I bet that's a difficultly in getting the flow rates right for a particular speed.

So making it a passive system not only simplifies it, it means that air only gets blown through at high speeds- when you dowant it.

Yes, very good point. In contrast to aircraft systems, the effect is being applied at relatively high rather than low velocities which is why you do not need to pump. A dedicated pump system would be easier to control, but not worth it for the weight. And as you said the engine exhaust is no good, either.

For me, the calibration of this passive system looks like it might be quite challenging.

And McLaren's 'scoop' from last year - isn't this wing just a development of that?

EDIT: Yes, I suppose this is like a large scale version of the scoops seen last year, although those slots where much shorter and fatter. What are the rules with these? Are they restricted in width?

I think, in general this is slightly different than a multi-element flap arrangement. Agreed, it's this sort of layout between the two main elements of the wing, but if that slot is blowing then it's a much more focused output more similar to a blown flap.

The Ferrari has such a slot:

[astracrazy]

Got this pic off the other forum

Never noticed the holes in the floor under the sidepod

[horse]

Sorry to harp on, this is probably getting a bit boring, but I was thinking with this system they could blow both the main element and the flap simultaneously. If I squeeze my eyes together tightly I can just make out another slot in the main element.

[Pup]

And McLaren's 'scoop' from last year - isn't this wing just a development of that?

EDIT: Yes, I suppose this is like a large scale version of the scoops seen last year, although those slots where much shorter and fatter. What are the rules with these? Are they restricted in width?

I think, in general this is slightly different than a multi-element flap arrangement. Agreed, it's this sort of layout between the two main elements of the wing, but if that slot is blowing then it's a much more focused output more similar to a blown flap.

The Ferrari has such a slot:

There's a difference, though. Look at the Suzuka pictures from last year - the 24 had a scoop, but no obvious outlet. Is there not the faintest outline of a slot on the bottom element here, or am I seeing things?

[horse]

There's a difference, though. Look at the Suzuka pictures from last year - the 24 had a scoop, but no obvious outlet. Is there not the faintest outline of a slot on the bottom element here, or am I seeing things?

I think that slot is identical to Ferrari's. Just seems to be a hole in the main plain.

http://www.formula1.com/news/technical/ ... 0/662.html

F1 technical described it as a "Third element"

http://www.f1technical.net/development/246

Seems like this solution can only be used for a short section. Perhaps because it is not visible from the front the blown flap can be used for the whole wing?

EDIT: I don't know, you might be right though, Pup, I can't find a good picture of the outlet for last years McLaren wing, just the inlet.

[Pup]

I think it was a hole originally, just like Ferrari and Toyota's.

But then one day it disappeared...



Alien abduction?