Mclaren Mercedes MP4-25

[Pup]

OK, I agree Pup, we should end this blown/not blown/stall thing. We know
too little about the MP4/25 design to go further. It'll be just iteration of things. We may see/not see later during the season who was wrong/right.
Let's find another detail on MP4/25 to discuss. There's plenty of it

I'm not opposed to discussing the wing at all. It was just clear that SLC had no idea that we'd already gone over a lot of what he was saying. I agree with him, btw, on everything but the on/off switch.

[Pup]

EDITx: This is my feeling for it, if you disrupt the normal airflow on the left by injecting airflow on the right, you actually make the drag worse by redirecting the vector more in the plain of motion of the car.



Ok, you lose some of the DF vector acting in the wrong direction too, but I can't see this system being all gain and no loss. I guess the multi-element wing is a tad more complicated than this too. I think the assumption is that injecting into the suction side, would not disrupt the airflow about the wing, and that's where I would contest it unless you're energising the boundary layer to avoid separation.

I think this diagram is more like it, since the angle of attack is more accurate for the upper element. Like I said, I accept that stalling the wing is a good thing, even though I don't really understand it. But I'll give you my take on what I think is happening, and then maybe SLC can educate us both. There are two types of drag, form and induced (and friction, but who cares about that), and what you've shown as the downforce vector is what creates the induced drag, which happens when the resulting vector isn't perpendicular to the motion of the wing. So you can resolve your DF vector into a horizontal and perpendicular, and the horizontal is the induced drag. OK, you probably know that. My suspicion as to why stalling the wing works is that the induced drag is actually much greater than you've shown and the form drag is much less. Therefore, when you stall the wing, the decreased induced drag more than makes up for the increased form drag. How much more? 10-20kph more, according to SLC.

At least, that's the only way it all makes sense to me.

[horse]

There are two types of drag, form and induced (and friction, but who cares about that), and what you've shown as the downforce vector is what creates the induced drag, which happens when the resulting vector isn't perpendicular to the motion of the wing. So you can resolve your DF vector into a horizontal and perpendicular, and the horizontal is the induced drag. OK, you probably know that. My suspicion as to why stalling the wing works is that the induced drag is actually much greater than you've shown and the form drag is much less. Therefore, when you stall the wing, the decreased induced drag more than makes up for the increased form drag.

Yeah, I don't think my vectors are right there, by any means. Too much of a rush job. My first diagram would seem to show the combined force would produce lift! I think in actual fact, if the flow was that well attached then this drag vector should be quite small in comparison to the lift vector, which you are right, is aligned in such a way as to add to the measured drag in the horizontal plain. I think ideally we'd keep the attached flow levels of drag whilst decreasing the lift vector. If the flow is normally attached then detaching it will make a lot of messy flow behind it and will cause a lot of drag, though, like the second diagram. However...

@Ringo, perhaps I am wrong about the condition of the flow behind the wing? If it is already separated at the injection point, then my ideas don't really hold and perhaps injection into the flow (but not in a blown flap sense) would have a positive impact. I'm well out of my league now though.

EDIT: This might be a better attempt. Dashed lines show the resultant in the direction of interest.

[Pierce89]

I think we've fairly well established that there is no intent to stall anything.

This is not in any way well established. Why do you think there was such a big hoo-ha about flexible wing elements and closing up of slot gaps in 2005-2006? Because they stalled the rear wing.

The rear wing produces a fair amount of downforce, and a fair amount of drag. Without getting into any semantics regarding pressure drag, induced drag or whatever, just look at the sections of a typical F1 top rear wing - the average camber line is extremely angled (practically vertical).

The total load vector of the wing assembly has a significant horizontal component - this, in its simplest form, would be called pressure drag.

If you stall the wing the load vector reduces in magnitude by a relatively large amount - and obviously therefore the horizontal component of this vector (the pressure drag!) is massively reduced.

Yes you lose downforce, but nobody gives a crap about downforce at 300kph down a straight. Drag reduction is golden.

This is not something that can be argued - it is a fact. I'll repeat it in case someone missed it. Stalling the top rear wing of an F1 car reduces the car's total drag. This is not the case for a relatively lightly loaded aircraft wing in steady level flight, before someone digs up some random paper on it.

Rumour has it McLaren are using some sort of pressure sensitive circuit (google "fluidic switch") within the roll hoop to control the mass flow down the engine cover duct - it can be extremely precise in its velocity switching effect, and that the mechanism can be controlled (but obviously not in any active or electronic way - this would be very illegal) via the driver's leg or knee.

Dude Please!!! Increasing energy under the wing(with a stream of air) to decrease seperation would give increase in effiency. More benefit over entire lap and much more plausible because it doesn't require near as much air as eliminating the low pressure zone would.

[Pierce89]

this is a terrible discussion.not a fact anywhere

[Raptor22]

"Nobody gives a crap about downforce down a straight at 300km/hr.."


Ok I give up trying to talk to you. There is a fundamental misunderstanding in your mind about what is required for a car to function at 300km.hr down a straight, autobahn what ever.

Firstly, you cannot stall one wing element. The lower winn just off the top of the chassis is de-coupled to some extent but the element that makes up the upper wing are all coupled.
Stall one element and the whole wing, including the lower wing stalls.

Stall teh entre wing and the diffusor chokes resulting in a rapid increase in pressure under the car and this makes it extremely unstable.

Someone tried to debunk my effect being similar to removal of the rear wing and missed the point. The oint is that both cases result in a sudden and massive disruption in flow around the car. Thats why when the wing falls off, cars spin off the road or at lest gives the driver more than hand full of fish tailing to contend with. Downforce at high speed is vitally important. If this stalling concept was so fantastic why do they not run stalled wings at Monza...? I rest my case.

Ringo, shooting a hole in the wing does not result in a pressure equalisation. for that to occur, you would need to shoot enough holes into the wing so that the surface area of the wing is reduced sufficiently to not suspend the mass of the aircraft so its not a good analogy. even if I drill a hole through the M4/25 rear wing, the wing will still produce massive downforce because.

- the pressure equalisation does not occur
- there is a still a massive vertical displacement of air /sec.

I also tested this out one of my park flyers. I drilled holes into the wingeverywhere this morning and took it for a flight. Hey its still flies... it requires a bit of up trim but it still flies. So how do you explan this? The airflow over the wing is fast enough for pressure equalisation not be significant.

and no I do not believe in the stalled wing concept and I never will. Its science fiction and I think it was created by James Allen.

No body that would like to move through the air wants to "Stall", not even bee's.
If Stall was desired, mother nature would have invented it. Wait, actually she did, when birds land they essentially stall their wings and use it as an airbrake.
Other useful applications of stalled wings are airbrakes on aircraft.


Stall is useful for slowing things down, not speeding them up.

right now I'm off to the Hobby store to buy new wings for my Wilga

[Pierce89]

http://scarbsf1.wordpress.com/2010/02/1 ... /#comments

Macca had a blown flap at MONACO 09. It's for increased downforce not reduced drag. @SLC: you're wrong. drop it.

[kalinka]

I agree, somenone said before that a stalled wing is as aerodynamic lika a brick. Stalling an aeroplane wing causes the airflow to detach from the surface of the wing, and the plane fell off the sky. Stalling the wing is the most dangerous thing you can do with a plane.
For an F1 car, I imagine the situation that if the rear wing stalls, then you can loose even the diffusor-s downforce, because the ride height increases, since there much less pressure that presses the rear end down . To have the diffuser work, you have to maintain ride height. In the same time, front downforce stays almost as it was, worstening the situation even more. Maybe you can go down the straight at 300kph in this way, but imagine that you want to overtake at high speed, or you have to take some fast manouvres ( debris on track,etc...). In that situation, with no rear downforce you cannot stay on track.

Cornermarker , you need downforce at the high speed corners too . That was the main prboblem with last years Mclaren, they were losing downforce at high speed corners. You have low speed cornering, high speed straight, and high speed cornering. You must balance the aero of the car so that you don't lose too much in neither of these sections of the track. On special tracks like monza, you can do that ( Mclaren was indeed fast there in 2009 ).

[tok-tokkie]

I subscribe to the blown flap theory & don't believe in the stalled wing hypothesis. I calculated the velocity pressure at 200 kph to see what was available to power the blown flap.
http://en.wikipedia.org/wiki/Velocity_pressure

q = 1/2 ρ v²
200 kph ~= 56 m/s
q = 1/2*1.2048(56*56)
= 1 854 Pa
= 0.02 bar

That really is insignificant.

Have I missed something? OK so the air pressure behind the wing is less than atmospheric. The inlet area is considerably greater than the outlet (& McL have been playing with that) - how do you quantify that?

[kalinka]

I subscribe to the blown flap theory & don't believe in the stalled wing hypothesis. I calculated the velocity pressure at 200 kph to see what was available to power the blown flap.
http://en.wikipedia.org/wiki/Velocity_pressure

q = 1/2 ρ v²
200 kph ~= 56 m/s
q = 1/2*1.2048(56*56)
= 1 854 Pa
= 0.02 bar

That really is insignificant.

Have I missed something? OK so the air pressure behind the wing is less than atmospheric. The inlet area is considerably greater than the outlet (& McL have been playing with that) - how do you quantify that?

I pointed out before, that some research data says that in blown wing case, the most important thing is not airspeed, but the amount of air you can blow on it.

One of the research papers says :

"Lift coefficient increased appreciably with blowing at low values of the parameters, and then tended to level off as blowing was increased."

I am not an expert but if you have a big inlet and a smaller outlet, I think the pressure at same airspeed must be higher at the outlet, beacuse the same amount of air at same speed only can exit at higher pressure.

On the other hand, you have increased pressure ( because of speed ) at inlet, and ( probably ) low pressure at the back of the car. So that increases the pressure difference even more. Of course you must have some drag increse i I think. In your calculation there is no detail about intake/outlet size. You must consider it too, though don't ask me how to do that

[mstar]

we should see some new components on the car today =D> , i wonder if we can spot them...

[cornermarker]

Thanks for the reply, kalinka. What I'm envisioning is a system that makes your wing one ideal for every section of that particular track, once calibrated. In low speeds, it causes the wing to behave more like you have a Monaco setup. At top speed, it behaves more like a Monza wing. The act of altering the pressure at the rear of the wing positively or negatively would be like automatically altering it's angle of attack slightly.

Again, this would be adaptable. So at a track like turkey with very high speed turns, you could bias it for high downforce (suction) for all but the very highest of speeds reached, at which point, it would go neutral, or ideally apply slight positive pressure.

[Richard]

This thread is going to be bigger than the UsF1 thread before the first race. Imagine if the car gets an updated part

Such as removing the fin in Bahrain?

[Richard]

Also, whilst we are on the rumour front, this stalling system has apparently been in the works for the past three years...

we should see some new components on the car today =D> , i wonder if we can spot them...

Sources?

[mstar]

we should see some new components on the car today =D> , i wonder if we can spot them...

Sources?

Mclaren press release yesterday

"Despite starting the third week of pre-season testing, today was the first time that the team had been able to follow a concerted, progressive day of set-up work in consistent conditions.
After yesterday’s rains abated, Jenson was able to spend the majority of the day pursuing a consistent path with mechanical set-up development, despite the presence in the afternoon of an increasingly blustery wind.
Jenson declared himself happy with the day’s progress, and his engineers have been extremely pleased with the extent to which he has been able to establish himself within the team, and the depth and scope of his feedback.
A few minor components will arrive overnight for evaluation tomorrow, but the main aim of the programme remains a continuation of today’s set-up development work."