Mclaren Mercedes MP4-25

[meves]

It is definitely a stalling mechanism. Yes, this will decrease the effectiveness of the diffuser but at 300kph down a straight you don't really care about the absolute downforce level you are producing - as long as you can shed 10-15 pts of Cd.

And yes, it is driver operated. Somehow.

Here's a question- does the total drag of the wing/car decrease once the wing stalls?

(if it does then....)

It seems to me that if blowing air through the flap tends to delay the speed at which the trailing edge of the wing stalls, the team can then actively control when the wing is stalled.

If the system is purely passive then this will have to be set for each track; ie China you will want less drag down the long straight, so stall it earlier, whereas Silverstone with long fast turns will want more high speed downforce so stall it later.

The possibilities are even more exciting if the team can actively control the flow of air while driving; down any straight they could stall the wing, whilst still keeping it going in high speed turns.

As usual though, it's conjecture and probably banned ideas from me... oh well....

And so we've gone full circle on this topic and we're back to Goonies elusive "dead zone"

[Pandamasque]

That would be just a movable aero device. On the other hand they can use a flexible one. I don't think there's a FIA test for flex in the internal aero devices

[myurr]

That would not happen if the cooling systems of the car were working properly

I can see where you are coming from but those parts weren't just thrown together - the holes for them were designed in from the launch, and the parts themselves are all properly made, not botched together, and in use from day 1 of testing. Seems to me like planned testing to see the optimal configuration for different conditions.

[kalinka]

Forget the dead zone. Read the forum several pages before me and other forumers found scientific data about blown wings. It's nothing about a dead-zone. At least nothing to do with the rear wing. For the diffuser : it still may be a dead zone.

[bonjon1979]

They haven't. A German site reported that they may have overheating problems after seeing the slots on top of the sidepod appearing during the very first test. They assumed it had something to do with overheating issues. None have been actually confirmed and there's been no reports of it after their long runs.

Permit me to have a different opinion . It is not the total number of the exits around the car body but the fact that the team has been changing them all the time , testing different cooling options. Judge for yourself .









That would not happen if the cooling systems of the car were working properly

In every one of those cases those outlets have been placed in areas where their is a changeable panel. The parts aren't botched jobs and holes aren't being cut into the body to alleviate any problems. This seems to be something that is planned rather than as a result of any unforeseen problems.

[Richard]

It is not the total number of the exits around the car body but the fact that the team has been changing them all the time , testing different cooling options. Judge for yourself .

<snip>

That would not happen if the cooling systems of the car were working properly

I nearly agree with you, but would not say it is evidence of cooling failure. We can see they are trying out different methods for cooling the car. That does not say it is working properly or not. All we can say is that the team think it is a higher priority than other matters. That could be because:

- The major aero parts are working, so the body shop has spare capacity, so they are kept busy producing different cooling arrangements
- The cooling is awful so everything else is on hold while they try to fix it
- Most likely a mix of the above

The important thing to read into this is that McL are not trying out manic wing and diffuser configurations this year. They seem to have time to try out a variety of cooling ducts . … phew!

[mcdenife]

Bar555 wrote:
That would not happen if the cooling systems of the car were working properly

I not sure I agree and I think you gave the answer yourself:

...to find out if the cooling needs are fullfilled or not .

ie since, as you said, the sidepods are now really very compact and as this is testing then surely now is the time to analyse different solutions required over the course of the season.

[meves]

They wouldn't be able to vary the airflow through that vent either through flexible bodywork or a driver adjustable flap, fortunately the FIA have defined bodywork as

Bodywork :
All entirely sprung parts of the car in contact with the external air stream, except cameras, camera housings and the parts definitely associated with the mechanical functioning of the engine, transmission and running gear. Airboxes, radiators and engine exhausts are considered to be part of the bodywork.

And sections 3.17 and 3.18 are quite clear on the amount of flexibility allowed in the bodywork. Also it gives the FIA the ability to change test at any point meaning that if it was flexible or driver adjusted it would likely be banned pre the first race.

I would guess it's purely fed with an air stream, hence the need for some of the blocking off earlier in the tests to see what affect it has.

[TheMinister]

Kalinka, you sure about that paper? It seemed to be talking about leading edge blowing jets, whereas we are jets more on what would be the 'top' of the wing. You wouldn't happen to have an actual copy of the full paper?

And yes, we do always seem to end up going in circles. Bit like our precious sport really

EDIT- re meves; yep, seems to me that my idea is true (which it probably isn't) then you'd tune it for the track; so the wing stalled at slightly faster than you'd take the fastest high speed corner.

[Raptor22]

When air flow leaves a wing it reverts to atmospheric pressure. What I think we are seeing is typical of a denser fluid medium being deposited on the trailing edge of the wing as it leaves the wing surface.
this is probably a function of the surface tension of the liquid fluid and the air density and pressure interaction that occurs here.

Ah, right, I think I have witnessed that before, yes, thanks. Are you saying this is happening at both the trailing edge and the slot or just the trailing edge? I suppose I'm pushing for whether you think the flow-viz supports a blown flap there?

Also, what's with the red flow-viz? Do they think we're being too nosey, or did they just run out of green? It'll be hard to make out on a red wing anyway.

That diffuser outlet is enormous, isn't it?

Good Question.

frm past experience, the flow vis is usually more heavily depoisited where flow is most dense. ASthe pressure drops less paint is deposited or more is carried away and ends up in the air. My expereince in this is with supersonic bodies and their control surfaces but I think the principal of more heavy deposits = denser air flow remains.
At the blow vent on the wing you should see more heavy deposits which is consistent with the pictures. I'm not sure that the flow vis paint is being used absolutely correctly in this application because I read somewhere that they have cut it back with paraffin which will reduce the viscosity of the paint. I think hthey are using it purely for indicative reasons and hence the lines of deposition are exaggerated (or that could be intentional)


Ya i was quite surprised by the size of that diffusor. Normally bigger is not necessarily better with diffusors. the Size has to be modelled on the amount ofgas to be scavenged and the desired pressure size without shock. this one seems too large and I am not convinced about its efficiency.
Also, the part of it thats actualy sealed is about the same size as the Mercedes and Red BUll, which suggests that they got the basic working diffusor volume right and are just looking for more control over flow else where.
they could be using Exhaust air deflected upward to energise the flow out of the diffusor but again its effect has to balanced against whats happening upstream.

With Diffusors, the volume or mass flow of feed gas determines the effective size of the diffusor. Its no different with an F1 car. SO they either have a lot of air going under the car and then expanding it as much as possible, but there is an upper limit before the drag created by the air rushing back to fill the void once the gas exits the diffusor becomes prohibitive. Or their diffusor is not as big as they would like us to believe.

If they are looking for Newtonian 3rd law gains ( to every action there is an opposite and equal reaction) through directing as much air as possible vertical then its not the most efficient way to go.

I think once we see an underbody image of the car it will all start to make more sense. Right now the car is incredibly interesting and makes for really great conversation, but theres a few things that just don't add up.

[segedunum]

...to find out if the cooling needs are fullfilled or not .

ie since, as you said, the sidepods are now really very compact and as this is testing then surely now is the time to analyse different solutions required over the course of the season.

I don't see how you work that. They'll certainly be taking some measurements, but they wouldn't need to be doing that and they wouldn't be creating new holes in the bodywork if the cooling was actually working properly. That's what bar555 is saying. They're not doing this for the goodness of their health.

Mind you, it doesn't seem to have caused them any reliability mishaps so far..............

[mcdenife]

segedunum wrote:
....but they wouldn't need to be doing that and they wouldn't be creating new holes in the bodywork if the cooling was actually working properly.

Exactly the point, they are not creating new holes in the bodywork. As myurr said:

those parts weren't just thrown together - the holes for them were designed in from the launch, and the parts themselves are all properly made, not botched together, and in use from day 1 of testing.

It seems they are doing this more to ensure they do not have problems rather than because they have problems.

[kalinka]

Kalinka, you sure about that paper? It seemed to be talking about leading edge blowing jets, whereas we are jets more on what would be the 'top' of the wing. You wouldn't happen to have an actual copy of the full paper?

And yes, we do always seem to end up going in circles. Bit like our precious sport really

EDIT- re meves; yep, seems to me that my idea is true (which it probably isn't) then you'd tune it for the track; so the wing stalled at slightly faster than you'd take the fastest high speed corner.

Yes, I'm pretty sure, because you can google the problem and will find more than 100 other studies about same effect. (blown flap, boundary layer control...) What I posted here is just I think the shortest, clearest explanation. You can find studies with 20-30 pages and more diagrams if you wish. The blowing wing concept is all about anti-stalling the wing : sticking the airflow to the surface of the wing all the way to the end. So the rear wing may "stall" in case of high angle,and high speed situation, but here the "stall" means dramatically increased drag+low downforce because the airflow is no longer sticking to the surface of the wing. It's my understanding though.

[Pup]

Kalinka, thanks for the link. When we first got clued in on this, one of the theories was that the effect of the blown wing was simply overcome at high speeds, so that there wasn't any need for driver input. Or to be more precise, I had thought that at low speeds, the blowing allowed for a higher angle of attack/greater downforce, but that at higher speed, the whole effect collapsed and the wing stalled - sort of a combination of what you're saying and the stalling idea. With only the paper's abstract to go by, I don't know if it supports this idea or not - though it sounds as if it might. Their conclusions seem to be based on low angles of attack, which is certainly not an F1 wing.

But I have to add that I have still never gotten the concept of stalling a wing or diffuser for gain. Physics 101 just never prepared me for stuff such as that. So I simply trust those here who tell me that stalling on the straight is A-OK.

On the other topic du jour, I really do not think that Macca are having any cooling problems whatsoever. As its been pointed out before, the fiddling around they've done with inlets/outlets looks pre-planned, looks to have little to do with engine cooling, and to me at least, seems like fairly piddly stuff in the larger scheme of things.

Though it would be nice to have something to talk about other than the Wing of Circular Debate™ (or is it a Hot Air Circulation Control Device™?).

[Pup]

Also, while I don't think we can completely discount that this thing might be controlled somehow, I have to say that I hope it is not, regardless of how clever such a control device might be. I'd like my team to win on merit, and I certainly don't want to see this blow up into yet another scandal.

Having said that - and eager to shift the talk to some other part of the car, even if it's related - one thing we haven't discussed much is the "little" exhaust over the tail light. I guess we've all taken it's purpose at face value, with perhaps there being some added benefit of providing air directly over the diffuser. But I'll just throw this out for discussion...

This is an area of pretty low pressure, right? And I'm guessing that the pressure there decreases with speed. If so, then could this be used to control a flap or valve, using only the speed of the car as the trigger? Specifically, in regards to the blown wing, could the suction at this point be used to move a flap that would then direct the flow of air from the rear wing flap into this exhaust vent itself (or elsewhere - out of the engine cover slit, for example)? I'm thinking as I'm typing here, which is dangerous, but what the hell.

Taking it one step further, would there have to actually be a flap? Could there be one inlet, but two exits, and depending on the car's speed and the relative pressures created cause the air to flow one way or the other? I guess something like that would only work if the flow of air needed on the rear wing were really really small, so I guess not.

Oh! Or maybe the driver changes helmets mid-straight, causing the airflow to... Oh, sorry, wrong forum. I'll be over at Atlas if anyone needs me.