Reducing the drag of a two element wing through stall

[ringo]

About Yaw, normally the wind speed is always in the direction of heading of the vehicle.
Yaw in terms of the wind direction is experienced when the car is sliding or drifting and the longitudinal axis is at an angle to the heading. For example if piquet is sliding of the track sideways into the tyre barrier.
Even in a turn, the wind is still considered to be parallel to the heading. Though teams will make considerations for transients.
Then there is side draft from breeze, that is also like a yaw condition.

[Pup]

Before we jump to conclude on the blowing. There has to be an indication that the upper element is much steeper than the end of 09 upper element.
If we consider that the angle of attack does not change, stalling is not an issue if the element is at an angle where it is optimal, which could be similar to the 09 wing.

I agree, but keep in mind that they were using a rudimentary form of this at the end of last year as well using a slot. The most noticeable difference between their slotted and unslotted wings was the relative size of the second element - it's chord was much larger. EDIT - that's wrong, actually. The second element got smaller when they added the slot, and the bottom element got larger - which of course makes sense, since it was the bottom element that was being blown.

The base bleeding concept is the "normally closed" theory, where the wing is "turned off" by blowing the jet. In this case the wing is normally not stalled and only stalled at high speeds.

...

In the normally closed theory, the one that I and SLC have not thrown away as yet, suggests if the jet stops blowing, the wing will be in no danger of stalling because it is normally in an optimal position.

OK, fine - but I've yet to see anything to support this theory. Have you?

[Pup]

I am going to make some amendments to my wing and get the flow attached with a bridged wing.
The FIA regs should have some insight to the maximum thicknesses of the wing profiles, and i will work from there.
I will through in something like a diffuser as well.
I will repeat the experiment and see what happens.

Sounds like a plan. A couple things I'd look at are the camber of the main element, which seems much greater on the McLaren; and the chord of the second, which seems much larger on the Mac.

And I still suspect that whatever is going on with the top element is also happening on the bottom one, only we can't see the slot because of it's location.

[PlatinumZealot]

That is what I was saying from the beginning. The f1 wing does not change it's angle to he airflow so we can not assume that stalling makes drag in a similar way to how it happens in a plane wing.

This is because as a plane wing AoA increases it gets more perpendicular to the flow the frontal area increases which is a huge factor for drag. We can not apply this train of thought which is relates angle of attack to stall and drag to the formula 1 wing because the angle of attack and frontal area is always the same.

The stall seems to be desirable so that is what we have to investigate; Stalling the fixed wing and the resulting Lift and drag.

What also needs to investigate is how can Blowing OR NOT Blowing (at the different angles) stall this fixed wing.

[Pup]

Yes, yes, yes - thank you. There is this ingrained reluctance for many to accept that a stall might be beneficial. I can certainly understand why, but like you say, these wings are fundamentally different to textbook fare in many ways.

The blowing/not blowing/sucking/blowing the opposite direction/vibrating/gap closing discussion is interesting and important to be sure - but secondary to the basic question of why stalling the wing might well be beneficial to lap times.

[Raptor22]

Stalled flow at low speed....?? Yes perhaps at 60-80km/hr in the pitlane, but here mechanical grip is more important anyways.
where the wings need to efficient is from around 140km/hr to +300km/hr since this is the zone where the aerodynamics really needs to work at it best. Most f1 type wings will have uncoupled flow or stagnated flow at low speeds. However the McLaren wing will not be stalled until the blowing kicks in. The blowing is there to delay the stall till beyond the speed that the car is geared to be capable of for a given circuit. the wing will still function like any other well designed wing.

No offense intended, but I think you have a fundamental misunderstanding about how the setup is supposed to work. The blowing prevents the stall - it does not cause it. And if the wing is supposed to stall on the straight, at high speed, then it certainly would be stalled at lower speeds. So the blowing/sucking/whatever (it's blowing) would prevent that, and then it is cut off or disrupted somehow along the straight.

That, of course, is if you believe the wing is supposed to stall on the straight. If you don't, then the theory is the same, but the wing is blown constantly, never stalls, except perhaps at very low speeds, and the benefit is simply greater downforce and/or less drag.

No offence taken because I do have an understanding of what is going on with the MP4/25 wing. There is no magic or f1 specific rule book for F1 wings. these are wings, wings are wings, they all obey the same rules.
The fundamental difference between aircraft wings and F1 wings is that if an aircrafts wing stalls people die. If an F1 wing stalls, there still 4 bits of rubber holding the vehicle to the earth. Beyond that there is no difference.

let get a belief reference here;

1) I do not subscribe to the driver knee on off valve. Thats science fiction. the person who proposed that is strangely quiet...
2) I do not believe that a stalled wing is desired in any form here where aerodynamic grip is required.
3) I believe the blown flap is being used to increase the efficiency of the wing at high speed and to reduce drag under this operating condition.
4) I believe the wing is designed to keep the boundary layer attached through the useful aerodynamic speed range.
5) I believe that at low speed, all F1 rear wings are operating with a sub optimal flow. Hence in the MP4/25 there is no opportunity to generate the pressure required to drive the flap blowing unless there is a feedback mechanism connected to an EGR device from the engine. Therefore this wing (MP4/25) also operates sub optimally at lower speeds were mechanical grip is more important.


Now there is a misconception that at low speeds the F1 wing is stalled. Perhaps but I don't believe that it is since the wings leading edges at aligned to the angle of the flow approaching it.
Just beneath the feed tube the leading edge of the wing has an upward curl indicating flow is falling off the sharkfin onto the wing. At its edges at the end plates the leading edge is closer to a zero degree AoA since the flow here is more parallel to the ground.
The 2nd planes leading edge does not operate at a very high angle of attack to the flow approaching it either since this flow is influenced by the main element. So no I do not believe the wing is stalled at normal low racing speeds. Perhaps below 60km/hr it is but then most high performance f1 wings will have an optimal speed range within which they work most efficiently.

At these speeds blowing the flap is not possible. where is the energy coming from? Divine intervention? Is god sitting on the shark fin blowing air through it or are you suggesting a pump is being used?

so what the blowing is achieving is moving the efficient speed range from lets say (that means I am thumb sucking to illustrate a point) 80km/hr to 300km/hr to a more useful 80km/hr to 340km/hr.

[tok-tokkie]

Thanks Raptor. That is my uninformed take on the matter also but I could not have expressed it that clearly.

[TheMinister]

The basic question of why stalling the wing might well be beneficial to lap times.

Basically what we've got on the Mccy is a mechanism by which the rear wing could be set to stall (probably not fully, probably only at the top) at a given airspeed.

This may have been done before, with the bendy ferrari wings; although it is impossible to be certain exactly what they were doing.

Nobody seems to have a good answer as to why stalling will decrease drag, but nobody seems to be able to absolutely prove otherwise.

I'd absolutely love it for this rear stalling wing thing ( ) to be true, please Mr Aerogods make it so...

On a side note; aren't these forums just fantastic? This kind of debate and discussion is absolutely fascinating, long live F1 Technical!

[TheMinister]

Ducting air onto the rear wing in a controlled fashion, (i.e. mechanical valve) thereby stalling the wing at high speed presumeably reduces downforce. Usefull on the straights??
Could that work?, more to the point is it legal?

Dude USF1 are not going to make the grid, it's cute that you are so keen but you really are not going to build a car. Why not try lotus, think they may still be hiring?

[Raptor22]

valid reasons have been gven why stall is not beneficial, but some want to believe in it because the idea is so fantastic. Sort of like time travel or faster than light transportation.
Rear wing stall is quickly evolving into a religion with the real F1 engineers laughing in the pub afterward.

what is even more fascinating is that some are willing to believe that there is the magic wand in the cockpit that can switch the device on or off. All this with a little bit of ram air pressure and pipe length convolutions and diameter changes along the way.

Like any religion, you can explain that the is no proof of a deity yet many still choose to believe because it better to be wrong about something so fantastic that if ever proven incorrect the fall back position is common sense and laws of nature.

from non beleivers (non stall camp) perspective there is no fall back position except "I told you so" which is unlikely to be used.

In fluid dynamics, stall = not good.

In the fantasy world of F1 where anything is possible (perhaps even faster than light travel) fans just want to believe in massive technological leaps like was experienced in the late 80's.
It's tough to explain that F1 is not as technological as it would outwardly appear.

Look at it, Lotus ready to race an f1 car from zero to 5months?!
Virgin f1 in 7 months.

a lot of teh technology is bog std off the shelf aerospace technology.
What determines success is process and the amount of cash you throw at the problem.

Virgin tout CFD as the new technology while its been in use since the late 70's in aerospace, come on...

F1 is just a motorsport where more money is spent on very little gains. there is very very little real innovation in F1 anylonger and fans are just really hungry to find something, anything thats exciting to keep the imagination fired up.

What f1 needs is a more loose rule book. Then we'll see real innovations.

[hollus]

Fantastic discussion. I don't know if the wing stalls or partially stalls or doesn't stall at all, all I know is that since page 40(ish) in MP25 forum I have learn't a hell of a lot about rear wings. And the dicussion is even staying civil! Keep it up, boys!

We all agree that stalling a roughly horizontal wing like in an airplane is bad. Whether that is so bad in an F1, I don't know, but I would like the discussion to include both scenarios. Let's assume this is there to stall the wing and see what can come out of it. And let's assume that this is there to avoid it from stalling and see what comes out of it! Bring in more flow diagrams!

From a very philisophical and not so mathematical point of view, I'll consider a rear wing a single element flat panel at an angle of 45 degrees to the floor. By its mere being in the flow, high pressure will accumulate in front of it and low pressure behind. This pushes perpendicularly to the wing, thus the car is pushed partially downwards and partially backwards. I'll call these pressure forces. Now, the wing, if the airflow is attached, will receive air flowing horizontally at 250Km/h and produce air flowing at 45 degrees to the floor, presumably at close to 250Kmh along the wing plane. This air has thus now moving forwards at the square root of 2 less than the initial horizontal speed, or about 175Km/h. It has lost 75Km/h of horizontal speed (relative to the car, relative to the ground it has gone from stationary to 75Km/h moving forwards) and must thus be pushing the car backwards. This air is also now moving at 175Km/h vertically and thus it must push the car downwards. I'll call these flow forces. Do not dismiss flow forces, a F1 car travelling at 300Km finds in the order of 100Kg of air in its way every second, and we all know that it mostly pushes it all upwards.
Thus, looking at pressure forces, if you get more downforce on the car, you have to pay as more drag on the car. Looking at flow forces, if you get more downforce in the car you also must pay as more drag in the car. The relative magnitudes can vary of course and my very crude plank wing does not even try to capture it.
As I see it, if the wing would go from nice attached flow to a stall, be this total or partial, the pressure forces would likely increase (more downforce and drag on the car), while the flow forces would for the most part, dissapear, (less downforce and less drag on the car). Flow forces probably have a better downforce to drag ratio than pressure forces, but in the straight they are not so needed. The car would not lose all downforce, as it would not lose all drag. In stall, it gains more of both, downforce and drag from prossure forces, and loses both downforce and drag from flow forces. It is all a quastion of the relative magnitudes.

[chasefreak]

has that front snorkel changed again

[mith]

Looks like it did. I'm really curious what are they up to? I don't believe in all that 'active knee steering theory', but still why are they paying so much attention to that vent?

[Tbox]

has that front snorkel changed again

That's what I said but was rebuffed by someone saying that it was like that in Jerez.

Thast was a sideways angle, tho wasn't it?

[Shaddock]

has that front snorkel changed again

That's what I said but was rebuffed by someone saying that it was like that in Jerez.

It looks a lot flatter than in Jerez, this look like Mark 3

The pipe that comes off that snorkel has to pass into the cockpit and be squeezable in some way, or why bother putting it there. If you wanted to feed extra air to the rear wing/diffuser etc there would be better places to locate it than in front of the driver.