257 replies to this topic

[Guizotia]

There has been some discussion in the McLaren thread about how the McLaren rear wing works. Due to the long nature of the thread this discussion has been going round in circles for about 50 pages, so I created this thread for it.

The following is a summary of how the McLaren rear wing works.

Christian Horner was the first official figure to comment on it:

[McLaren] have a slot on [the rear wing] and they can pick up a lot of straight-line speed. I think it will get resolved before the first race. We've asked the FIA for clarification although I think Ferrari are probably more excited than we are to be honest.

Basically, if you stall the wing you take all the drag off it and pick up straight-line speed. It's something that's been done quite a lot over the years but with the wing separators you're not supposed to do that.

The basic assumption is that McLaren rear wing works by channelling air through the intake, into the rear wing and out of the slot on the rear of the wing. The question is what is this intended to achieve, which way does the air blow and how does this benefit the car?

Simple summary: McLaren have found a way to stall their wing to get less drag

The idea behind the blown slot is to blow air out of the slot at high speed, against the natural flow of the air, to detach the air flow, reducing downforce and hence drag. This might be described as a "stall" because this what you call the air flow detaching from an aircraft wing due to it's angle of attack being too high.

Now people will say that if you stall a wing you create extra drag. Things aren't this simple, for example, see this graph from NASA:



You can see that if you get the effective angle of attack right, you can reduce the drag by stalling. A two element F1 rear wing will behave very differently but the basic principle holds that a stalled wing can have less drag than an unstalled wing.



The air from the slot detaches the air that is travelling over the back of the wing, causing the same effect as a stall on an aircraft wing.

How is the air flow controlled?
AMuS makes the point that any automatic aerodynamic changes would contravene the rules, so the turning on and off of the device must be controlled by the driver. This brings up the snorkel rumours. See the following for a picture of the snorkel:

http://f1.gpupdate.n...catID=1102-4456

The snorkel is positioned just in front of the driver cockpit. The rumour is that air flow from the snorkel is controlled by the driver in an on/off by manipulating something with or positioning their knee, and either this air flow goes to the rear wing, or it interacts with the air box flow to the rear wing via some kind of fluidics switch.

Edited by Guizotia, 11 March 2010 - 23:47.

[mikerr]

What if there is a driver (or speed) operated valve inside that sharkfin ?

[Guizotia]

What if there is a driver (or speed) operated valve inside that sharkfin ?

A speed operated valve would help, as it would allow the effect to be turned off under a certain speed.

Edited by Guizotia, 09 March 2010 - 21:52.

[Guizotia]

Copied to first post.

Edited by Guizotia, 10 March 2010 - 12:04.

[dren]

I don't see how the blown wing would detach the flow if it is doing virtually the same thing as the split between the two rear wings, unless the direction of air that is blown is not what is shown in your picture.

Edited by dren, 09 March 2010 - 22:18.

[PassWind]

There are two sets of slots as well you can see there are slots in the bottom element as well.

[One]

Is the slit feeding the air jetting more towards rear direction? Or may be the air speed at the slit is way quicker than around it so that it cuts attached air on the back end of the wing?

Funny that Mclaren discovered it, rather than Red Bull.

[pup]

Edit: copied from the 25 thread, talking about the possibility that the main element of the wing is also blown...

It does look that way I must admit, but in comparison, where the shark fin meets the upper wing element, it begins to diverge so there is smooth curved 90 degree transition from the fin to the wing, I assume helps regulate the internal airflow. With the wing support strut there is no such design, which makes me reconsider the viability of a slotted main plane.

True enough. I'm prejudiced, since I was looking for the slot to be there. In my mind, if they are indeed switching this thing on and off, it would be much easier for them to do so with air coming up the strut, simply because there's a lot more opportunity around there for the necessary valve and connections. I think the upper element duct looks too tightly packaged for all that. Just an opinion, of course.

But do note in that pic I posted that the engine cover slot looks to be a dedicated duct of its own. Connected to what, I couldn't say for sure - but given that the fluidic valve in the example I posted earlier needs three outlets, and the fact that we've got three outlets right there (the wing, the engine slot, and the tail light outlet), I'd say there's certainly enough evidence to propose that they might be switching the lower element and not the upper.

Or not.

Edited by pup, 09 March 2010 - 23:12.

[pup]

And the pic, for you folks following at home...

[GhostR]

Question: When does a slot in a single element get long enough for that element to be considered two elements instead of one?

[Anomnader]

Question: When does a slot in a single element get long enough for that element to be considered two elements instead of one?

would it be a case of depth rather then length, its only 2 elements at one side, not all the way through,

[pup]

Question: When does a slot in a single element get long enough for that element to be considered two elements instead of one?

The overall length isn't important. What matters as far as the FIA is concerned is if the wing has both an inlet and an exit in any given section, outside of the 150mm zone in the center of the wing. If there is an inlet and an exit, then the wing is considered to have more than one "closed section". If there is either an inlet or an exit, but not both, the section is still considered "closed". The 150mm zone is there to allow for central wing supports, but the way it is written also allows for the teams to sneak in a third element; or, in McLaren's case, a duct which supplies the wing with pressurized air.

Edited by pup, 10 March 2010 - 01:03.

[TenienteX]

what about the drivers knee blocking/opening the intake of the "snorkel" allowing the whole solution to work?

safety issues anyone? reportedly the drivers body-movement decides if the rear wing works or not.

[Chomsky]

If the driver's leg movement is part of the aero feature of the McLaren then it could be banned. The thing is though is the driver really considered in the rules as an aero device (I mean they move their heads all the time).

p.s. FIA are dumb for banning the mass damper as movable aero device.

[Atreiu]

So, which is it?
- reduces drag on straights and allows for high downforce set ups, or
- creates more downforce without adding so much drag?

[JForce]

So, which is it?
- reduces drag on straights and allows for high downforce set ups, or
- creates more downforce without adding so much drag?

Neither as far as I understand it.

At low to medium speeds, it doesn't create any more downforce than if it wasn't there. The car is as it would be without it.

However at high speeds it eliminates drag, raising the top speed.

So I don't think it's about creating downforce, regardless of speed, it's about eliminating drag only at high speeds.

[Birelman]

Well, lets just prey and hope this thing is illegal, cus otherwise in 2 months we're gonna have a grid full of those ugly engine covers!!!!!!!

[Timstr11]

It has to be a passive system, otherwise it is very illegal.
So it can't be driver operated in any way.
It can't have a valve that opens and closes according to conditions (movable aero).

[Vegetableman]

.

(Some people want to argue that in fact the reverse is true, that the air blows faster at low speeds to keep the air attached to a steeper wing, giving greater downforce. There is one big problem with this idea and that is power. Aircraft blow air over their flaps to keep the air flow attached while landing and this takes a great deal of power. In fact that is why aircraft only do this while landing, because this is the only time they have the spare engine capacity to use to power the blowing.

This is not correct.
As I pointed out in the McLaren thread, which unfortunately we didn't get to discuss because there was 5(!) pages posted in the time between me posting and re reading the thread.

Aircraft have passive slots in the flaps which simply use the higher velocity air from the underside to re attach the turbulent air on the low pressure side.
This is what I believe the basic principal is behind the slot wing. It enables the wing to be run at a higher angle without stalling, ie producing more downforce. How they stall the wing at higher speed I don't know. Perhaps the gap chokes at a certain velocity...

Scarbs has run a good article on it explaining basically how it works but even he doesn't know how they are stalling the wing at high speed.

[Guizotia]

I don't see how the blown wing would detach the flow if it is doing virtually the same thing as the split between the two rear wings, unless the direction of air that is blown is not what is shown in your picture.

That's exactly the point. It's doing the same as the split in the rear wing used to do before the regulations increased the gap between them creating two distinct elements.

People used to use a split in the rear wing to cause the stalling. That's what Christian Horner refers to:

"It's something that's been done quite a lot over the years but with the wing separators you're not supposed to do that."

The wing separators he refers to cause the two element rear wing to have a big enough gap between the two elements to prevent the stalling effect of the air passing through the wing and detaching the air flow on the rear side at high speed.

By passing the air through the intake McLaren have achieved the same effect for one or both elements, while still satisfying the regulations around having a two element rear wing with a big enough gap inbetween the two elements.

Edited by Guizotia, 10 March 2010 - 07:51.

[Guizotia]

This is not correct.
As I pointed out in the McLaren thread, which unfortunately we didn't get to discuss because there was 5(!) pages posted in the time between me posting and re reading the thread.

Aircraft have passive slots in the flaps which simply use the higher velocity air from the underside to re attach the turbulent air on the low pressure side.
This is what I believe the basic principal is behind the slot wing. It enables the wing to be run at a higher angle without stalling, ie producing more downforce. How they stall the wing at higher speed I don't know. Perhaps the gap chokes at a certain velocity...

Scarbs has run a good article on it explaining basically how it works but even he doesn't know how they are stalling the wing at high speed.

I guess your understanding is better than Adrian Newey's?

I'm not sure why you find it hard to understand how they stall the wing at high speed. To me it's childishly simple, by ejecting the air from the slot at high pressure the air flow on the reverse side of the wing is detached. This is exactly what happens to an aircraft wing when stalling, except that in an aircraft wing the detachment is caused by the angle of attack going over a certain angle. McLaren do not have the luxury of changing the angle of attack, so this blown slot achieves the same effect. And as we see from the NASA graph and Christian Horner's comments stalling can reduce the drag if done right.

[Vegetableman]

I guess your understanding is better than Adrian Newey's?

I'm not sure why you find it hard to understand how they stall the wing at high speed. To me it's childishly simple, by ejecting the air from the slot at high pressure the air flow on the reverse side of the wing is detached. This is exactly what happens to an aircraft wing when stalling, except that in an aircraft wing the detachment is caused by the angle of attack going over a certain angle. McLaren do not have the luxury of changing the angle of attack, so this blown slot achieves the same effect. And as we see from the NASA graph and Christian Horner's comments stalling can reduce the drag if done right.

Quoting: Scarbs Blog

The steeper a wings angle, the greater chance of separation. To combat this aerodynamicists need to speed up the flow near the wings surface, to do this they split the wing into separate elements, this creates a slot. Which sends high pressure air from above the wing through the slot, which then speeds the local flow underneath the wing. The more slots the steeper the wing can run.

Last year BMW Sauber and McLaren ran wings with the narrow 15cm opening on the front of the wing, but this inlet diverged to make a slot the full width of the rear wing (normally within the main plane). This slot was aligned to send its airflow at an acute angle, roughly inline with the general flow over the wing. Again this was deemed legal as the slot made the wing profile an ‘open section’ only in the middle of the wing, where as the outers spans remained a ‘closed section’ albeit one with a “U” shape. With this design the slot could allow the entire wing to be steeper and not just the geometry in the middle 15cm of the wing.

The McLaren 2010 wing uses a slot in the flap (not the main plane), this time fed by the shark fin and an opening above the drivers head. If the teams’ protests about its legality are true, then the issue is that McLaren are using the slot to stall the wing.... This could be possible in several ways; one could be having the slot orientated differently to the airflow over the wing, if it were at nearer right angles to the flow it could blow hard enough to disrupt the airflow enough to stall the wing. Another solution might be that the slot blows at lower speed maintaining a clean airflow over the wing, then at higher speed the slot chokes with the greater airflow trying to pass through it, the slot no longer blowing stalls the wing.

I'm not sure if we're disagreeing on the principal of how it works or just our wording is different leading to two apparently very different conclusions.

[ferruccio]

That's exactly the point. It's doing the same as the split in the rear wing used to do before the regulations increased the gap between them creating two distinct elements.

People used to use a split in the rear wing to cause the stalling. That's what Christian Horner refers to:

"It's something that's been done quite a lot over the years but with the wing separators you're not supposed to do that."

The wing separators he refers to cause the two element rear wing to have a big enough gap between the two elements to prevent the stalling effect of the air passing through the wing and detaching the air flow on the rear side at high speed.

By passing the air through the intake McLaren have achieved the same effect for one or both elements, while still satisfying the regulations around having a two element rear wing with a big enough gap inbetween the two elements.

ok. it's beginning to make sense and if I understood it right, really not rocket science at all but just good 'lateral thinking' on Mclaren's part. If I understand it correctly, the homer simpsons in every team would go "D'OH" and we will start to see this appearing on other cars very quickly.

[moorsey]

It sounds to me like the "cyclone effect" so could the rear wing sponsor soon be "Dyson." lol.

[Chezrome]

If the driver's leg movement is part of the aero feature of the McLaren then it could be banned. The thing is though is the driver really considered in the rules as an aero device (I mean they move their heads all the time).

p.s. FIA are dumb for banning the mass damper as movable aero device.

+1. I think move-able aeroparts operated by the driver should be banned. But like you said: the massdamper was not a moveable aero device (furthermore, I am of the opinion that Carthago should be destroyed).

[femi]

ok. it's beginning to make sense and if I understood it right, really not rocket science at all but just good 'lateral thinking' on Mclaren's part. If I understand it correctly, the homer simpsons in every team would go "D'OH" and we will start to see this appearing on other cars very quickly.

You have to watch out though, Mclaren said the RB engineers would have very good idea of what has been done, very close but not close enough. My understading of that statement is Homer is close but not entirely correct with regards to Mclaren's implementation.

[Guizotia]

You have to watch out though, Mclaren said the RB engineers would have very good idea of what has been done, very close but not close enough. My understading of that statement is Homer is close but not entirely correct with regards to Mclaren's implementation.

I took that comment to mean that although they understood the general principal, the devil is in the detail.

I think Red Bull were just showing off that they understood it, kind of like they are saying "yeah we totally understand this, we just didn't think it was allowed" so they don't look like they have missed a trick.

Edited by Guizotia, 10 March 2010 - 09:04.

[Guizotia]

Quoting: Scarbs Blog

I'm not sure if we're disagreeing on the principal of how it works or just our wording is different leading to two apparently very different conclusions.

From your Scarbs quote:

"This could be possible in several ways;

one could be having the slot orientated differently to the airflow over the wing, if it were at nearer right angles to the flow it could blow hard enough to disrupt the airflow enough to stall the wing.

Another solution might be that the slot blows at lower speed maintaining a clean airflow over the wing, then at higher speed the slot chokes with the greater airflow trying to pass through it, the slot no longer blowing stalls the wing."

The problem with the second idea is that you have to blow the air very fast to get the effect. That's why aircraft only do it during landing when they have the spare engine revs. That rules it out for an F1 car. That only leaves the first solution.

[Vegetableman]

The problem with the second idea is that you have to blow the air very fast to get the effect. That's why aircraft only do it during landing when they have the spare engine revs. That rules it out for an F1 car. That only leaves the first solution.

I think you need to go back and re-read my explanation about the slotted flap on an aircraft. See My first post on the subject
It is a passive device. It works by using the air that is flowing over the flap generated by forward flight.
The active device is what you are thinking of. Bleed air from the engines is directed out (normally to the leading edge I believe) to help re-energize the boundary layer air.

I think the first explanation Scarbs gives is too simple, the other teams would have figured out how to do that by now.
This of course is just my opinion and I am no expert on F1 aerodynamics but I do have an understanding of aircraft principles.

[Guizotia]

I think you need to go back and re-read my explanation about the slotted flap on an aircraft. See My first post on the subject
It is a passive device. It works by using the air that is flowing over the flap generated by forward flight.
The active device is what you are thinking of. Bleed air from the engines is directed out (normally to the leading edge I believe) to help re-energize the boundary layer air.

I think the first explanation Scarbs gives is too simple, the other teams would have figured out how to do that by now.
This of course is just my opinion and I am no expert on F1 aerodynamics but I do have an understanding of aircraft principles.

OK I see you are talking about a third explanation, a slotted flap.

From Wikipedia:

"Slotted flap: a slot (or gap) between the flap and the wing enables high pressure air from below the wing to re-energize the boundary layer over the flap. This helps the airflow to stay attached to the flap, delaying the stall."

While it seems plausible, there are big issues.

Forgetting that it contradicts what Horner has said:

The slotted flap idea would work in an F1 car by allowing a steeper wing to be run, that would normally stall, but the device works at lower speeds to prevent the stall and maintain the downforce of the steeper wing.

It is inherently dangerous because the car only has sufficent downforce while the device is active. If the device fails the car suddenly loses downforce at the times when it is most needed.

Such a device would be instantly banned under safety grounds.

Edited by Guizotia, 10 March 2010 - 10:13.

[anbeck]

Now people will say that if you stall a wing you create extra drag. This simply isn't true. See this graph from NASA:



You can see that if you get the effective angle of attack right, you can reduce the drag by stalling.

The graph from NASA might prove the exact opposite: Drag is depending on the angle of attack. If you stall it, you have it just a little bit under the max. drag you had when the airflow was attached.

BUT: if you look at the curve you'll see that you can reduce drag significantly by reducing the angle of attack.
We know that, for the same level of downforce, F1 teams would like to have 4 or 5 elements, because each one can be put at a little angle of attack. But the FIA limited rear wing elements to 4, then to 3 and now to 2 elements. So teams have to run these two elements at a rather high AoA to get the same downforce. If you look at your graph, you will see that a higher AoA results in higher drag.

The purpose of the blown slot thus is probably not to stall the wing, but to simulate a 3-element wing, which F1 teams would certainly prefer over a 2 element wing. If the discussions about both elements blown would relate to what is really going on, McLaren would effectively run a 4 elememt rear wing, which would reduce drag even more.

I know that the NASA graph is just an approximation, but that whole stalling-thing doesn't seem as attractive to me as a "4-element"-rear wing.

[anbeck]

Forgetting that it contradicts what Horner has said:

I still believe it was a bluff on Horner's part.

[Tenmantaylor]

p.s. FIA are dumb for banning the mass damper as movable aero device.

True, but if the drivers knee is proven to affect airflow it's more of a movable aero device than the mass damper ever was.

[Guizotia]

I still believe it was a bluff on Horner's part.

Who is he bluffing and what would it achieve? It would just make him look stupid in front of the other teams.

[ferruccio]

The purpose of the blown slot thus is probably not to stall the wing, but to simulate a 3-element wing, which F1 teams would certainly prefer over a 2 element wing. If the discussions about both elements blown would relate to what is really going on, McLaren would effectively run a 4 elememt rear wing, which would reduce drag even more.

Yes, thats what Homer said. Mclaren's rear wing is designed to stall at upper speeds and the blown slots works to prevent it from stalling when they don't want it to, I think

[Guizotia]

I have updated my first post in this thread to reflect the discussion.

[Dragonfly]

The graph from NASA might prove the exact opposite: Drag is depending on the angle of attack. If you stall it, you have it just a little bit under the max. drag you had when the airflow was attached.
...............................

Wouldn't that little bit be enough to allow a 10 km/h gain, as it is claimed?

[anbeck]

Who is he bluffing and what would it achieve? It would just make him look stupid in front of the other teams.

Well, the most obvious would be to
a) provoke a reaction from Macca ("Nah, that's not what we're doing"), which would allow them to exclude certain solutions
b) hoping that CW comes back from his visit to McLaren, reacting to what Horner said, or even
c) hoping that some engineers Ferrari and Mercedes now try to figure out the stalling-thing, wasting time on it, while at RB they're up to it.

McLaren even said that the other teams are not quite up to it yet, so either this time McLaren is bluffing or Horner didn't quite get it right.

[anbeck]

Yes, thats what Homer said. Mclaren's rear wing is designed to stall at upper speeds and the blown slots works to prevent it from stalling when they don't want it to, I think

From what I followed on F1technical, you cannot design a wing to stall at a certain speed. But maybe what you mean to say is that the rear wing stalls at all speeds, but that at lower speeds the slot counter-acts it. I'm no expert, but in this case I don't know if the air pressure is enough at low speeds to accomplish this, because the slot is fed by by a rather small tube, and when it's to be dispersed over the whole slot, the air velocity should suddenly drop quite a lot. Though, managind the airflow, is probably the secret behind all this.

Still, I don't see how a passive system could tell whether the car is in Blanchimont or not.

[Guizotia]

The graph from NASA might prove the exact opposite: Drag is depending on the angle of attack. If you stall it, you have it just a little bit under the max. drag you had when the airflow was attached.

BUT: if you look at the curve you'll see that you can reduce drag significantly by reducing the angle of attack.
We know that, for the same level of downforce, F1 teams would like to have 4 or 5 elements, because each one can be put at a little angle of attack. But the FIA limited rear wing elements to 4, then to 3 and now to 2 elements. So teams have to run these two elements at a rather high AoA to get the same downforce. If you look at your graph, you will see that a higher AoA results in higher drag.

The purpose of the blown slot thus is probably not to stall the wing, but to simulate a 3-element wing, which F1 teams would certainly prefer over a 2 element wing. If the discussions about both elements blown would relate to what is really going on, McLaren would effectively run a 4 elememt rear wing, which would reduce drag even more.

I know that the NASA graph is just an approximation, but that whole stalling-thing doesn't seem as attractive to me as a "4-element"-rear wing.

You're kind of saying something, without saying anything at all.

You need to explain what effect your "simulated three element wing" has in comparison to a two element wing. I.e. what does it achieve and how.

[anbeck]

The air from the slot detaches the air that is travelling over the back of the wing, causing the same effect as a stall on an aircraft wing.

How would the air, moving this way, result in air flow seperation? Shouldn't more air here have the opposite effect, i.e., delay separation?
EDIT: Wouldn't this energise the boundary layer, to put it in other words?

In order to detach the air flow, couldn't the slot be working the other way round than everything here seems to suppose?
If you look at the 'feeding tube' in the shark fin, you would agree that it's rather in the top. And if you look where it is connected to the rear wing, it's quite to the top as well.

So couldn't it be that, instead of being 'in the flow' of the air that passes there, it is directed against the airflow, that is, downwards? Don't have a graphics program here, but just imagine the two yellow arrows at the slot not pointing upwards, but downwards.


Thanks, btw, Guizotia, for rescuing us from the MP4-25 thread and putting together everything in this digest

Edited by anbeck, 10 March 2010 - 10:40.

[anbeck]

You're kind of saying something, without saying anything at all.

You need to explain what effect your "simulated three element wing" has in comparison to a two element wing. I.e. what does it achieve and how.

I think I said something: shouldn't a 3-element-wing allow you to have the same amount of 'lift' with less drag, as the average angle of attack would be smaller?

I mean, what is the reason for teams wanting to run as many elements as possible, and the FIA prohibiting it? There's a reason for that. And McLaren might just aim at effectively claiming their 3rd element back.

[threep]

Another solution might be that the slot blows at lower speed maintaining a clean airflow over the wing, then at higher speed the slot chokes with the greater airflow trying to pass through it, the slot no longer blowing stalls the wing."

The problem with the second idea is that you have to blow the air very fast to get the effect. That's why aircraft only do it during landing when they have the spare engine revs. That rules it out for an F1 car. That only leaves the first solution.

Can you have a passive system which will self limit flow down a duct at a given car velocity? Absolutely, yes. There would need to be an orifice somewhere between the inlet duct and the outlet in the rear wing which would become choked given the right pressure drop across it. There is a ram air effect which will increase P1 (upstream of the orifice) as a function of vehicle velocity, whilst downstream of the orifice the pressure P2 would see a decrease in pressure as the outlet would be in a low pressure zone. So as the velocity of the car rises, P1 increases and P2 decreases until dP (P1-P2) is sufficient for choked flow. I don't think its difficult to achieve, I've used this on aircraft cooling systems to control flows in ducts under different flight conditions. I haven't done the sums but the P1/P2 ratio for choked flow for air is approx 1.7 to 1.9, which must be achievable with F1 cars going around 150-200mph. So you could design a duct/orifice to achieve choked flow at a predetermined speed, with different designs for different circuits. The air massflow under choked conditions is related to P1 only, so my guess is McLaren would have designed a nice ram air inlet for any such device to give them maximum massflow to play with when it comes to playing with the flow over the rear wing.

I have no idea whether you can get sufficient massflow to make all this work in practice, but a passive system which self limits flow at a certain vehicle velocity is entirely feasible.

Edited by threep, 10 March 2010 - 10:43.

[Guizotia]

How would the air, moving this way, result in air flow seperation? Shouldn't more air here have the opposite effect, i.e., delay separation?
EDIT: Wouldn't this energise the boundary layer, to put it in other words?

In order to detach the air flow, couldn't the slot be working the other way round than everything here seems to suppose?
If you look at the 'feeding tube' in the shark fin, you would agree that it's rather in the top. And if you look where it is connected to the rear wing, it's quite to the top as well.

So couldn't it be that, instead of being 'in the flow' of the air that passes there, it is directed against the airflow, that is, downwards? Don't have a graphics program here, but just imagine the two yellow arrows at the slot not pointing upwards, but downwards.


Thanks, btw, Guizotia, for rescuing us from the MP4-25 thread and putting together everything in this digest

Imagine the yellow arrows pointing away from the rear wing i.e. the air is being ejected at an angle to the natural air flow.

[anbeck]

Wouldn't that little bit be enough to allow a 10 km/h gain, as it is claimed?

You know, the thing is: McLaren might be running with their pseudo-3-element wing, which allows them to re-energise the boundary layer at the low-pressure side of the wing. This means, they can reduce the angle of attack, in comparison with other teams, which gives them the same cornering speed, but these 5-10 kph more due to lower drag.

The same gain, without the risk of having a stalled rear wing at the wrong place.

This seems much less risky than having an on/off-switch, which might pose a problem in Eau Rouge and Blanchimont, not to speak of the FIA, who has shown with the TMD what they're capable of. Even with a fluidics design, you'd probably have to have an input by the driver, who, with the exception of the front wing, is not allowed to influence the aerodynamics (apparently head movements have been defined as secondary, thus are allowed).

[anbeck]

Imagine the yellow arrows pointing away from the rear wing i.e. the air is being ejected at an angle to the natural air flow.

Would the pressure be high enough to make the air flow not being sucked to the wing immediately, thus making it part of the natural air flow?

It'd be cool if there were some engineers who can enlighten us as far as the forces involved are concerned.

If we forget the snorkel for a minute, and assume that the air for Macca's secret comes solely from the upper part of the airbox. What kind of 'amout of air' are we talking about? What is the ratio of the air intake surface to the slot surface? And could the air be sped up within the car by narrowing the tube so that, when suddenly the slot opens up wide, there is still enough pressure to disturb the natural flow? I just can't see the blown air coming through that tiny slot being able to separate the boundary layer, which is being sucked up in such a massive fashion that it generates enough negative lift to nearly make a car run at the ceiling (well, not really, but it's just to show the forces involved at the rear wing - which I don't see disturbed by that blowing).

To me it seems, as if helping to make the layer keep attached would involve much less force, you could practically just put it there and it would become part of the natural flow, which is all that is needed.

You know, personally I don't favor any explanation, I just want to discuss for the sake of the insight we might be gaining from it.


EDIT: I hope the guys from F1technical don't mind me linking to this image:
http://i1010.photobu...finvelocity.jpg

Original post: http://www.f1technic...=152403#p152403

It shows that any air blown through that slot would seem to become part of the 'natural flow'.

If I may quote user ringo from over there:

The flow momentum is so high that it takes about 3 times the free stream velocity to rip it of the element to stall it. The farther away from center the harder to stall as well.

I don't see McLaren coming up with that kind of energy.

Edited by anbeck, 10 March 2010 - 11:33.

[Guizotia]

So couldn't it be that, instead of being 'in the flow' of the air that passes there, it is directed against the airflow, that is, downwards? Don't have a graphics program here, but just imagine the two yellow arrows at the slot not pointing upwards, but downwards.

Yes that's a possibility that I don't think anyone has mentioned.

[Dragonfly]

You know, the thing is: McLaren might be running with their pseudo-3-element wing, which allows them to re-energise the boundary layer at the low-pressure side of the wing. This means, they can reduce the angle of attack, in comparison with other teams, which gives them the same cornering speed, but these 5-10 kph more due to lower drag.

The same gain, without the risk of having a stalled rear wing at the wrong place.

This seems much less risky than having an on/off-switch, which might pose a problem in Eau Rouge and Blanchimont, not to speak of the FIA, who has shown with the TMD what they're capable of. Even with a fluidics design, you'd probably have to have an input by the driver, who, with the exception of the front wing, is not allowed to influence the aerodynamics (apparently head movements have been defined as secondary, thus are allowed).

Yes. There are two interpretations currently on discussion as far as I can understand.
- reducing drag by relatively small amount with the help of stalling the wing at high speeds
- obtaining equal down force with relatively smaller AoA and thus smaller drag due to energizing the flow at the low pressure side of the flap

Edited by Dragonfly, 10 March 2010 - 12:00.

[dren]

That's exactly the point. It's doing the same as the split in the rear wing used to do before the regulations increased the gap between them creating two distinct elements.

People used to use a split in the rear wing to cause the stalling. That's what Christian Horner refers to:

"It's something that's been done quite a lot over the years but with the wing separators you're not supposed to do that."

The wing separators he refers to cause the two element rear wing to have a big enough gap between the two elements to prevent the stalling effect of the air passing through the wing and detaching the air flow on the rear side at high speed.

By passing the air through the intake McLaren have achieved the same effect for one or both elements, while still satisfying the regulations around having a two element rear wing with a big enough gap inbetween the two elements.

The thinner gap used before allowed the wing to flex at high speeds and become one wing which would then stall because you didn't have air feeding between the wings to keep the flow together on the back side.

The gap helps to feed air to the back side, keeping the flow together allowing for a steeper wing to be used.

The new slot (if blowing air in the same direction as the flow around it) would be doing virtually the same thing, allowing a steeper angle of wing to be used becuase the flow stays together.

The idea, which makes the most sense to me for a stalling blown wing would be that the wing needs the blown air to keep flow from separating, but at high speeds it 'chokes' due to the air duct not being large enough to keep up with the increased flow velocity on the back side of the wing, thus stalling it.

Edited by dren, 10 March 2010 - 12:21.

[dren]

Yes that's a possibility that I don't think anyone has mentioned.

That is what I was getting at with my first post...