Reducing the drag of a two element wing through stall

[McMacca]

From telegraph story:

“Basically, if you stall the wing you take all the drag off it and pick up straight-line speed,” Horner explained. “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. Our question ultimately will be: 'Is it clever design or is it in breach of the regulations’?”

Been doing it for years...

I would have thought so, go to track, fastest corner is 220 kph, set AOA on wing to stall at 230 kph, ta da! reduced downforce/drag and higher top speed on straights where you reach over 230 kph. =D>

[forty-two]

Yes it has been done - for many years. This is not in any way a new concept in F1.

Fabulous. How did it work in the past?

+1

We'd all be delighted to know!

[horse]

I would have thought so, go to track, fastest corner is 220 kph, set AOA on wing to stall at 230 kph, ta da! reduced downforce/drag and higher top speed on straights where you reach over 230 kph. =D>

Yeah, fair enough. It's a bit confusing though because Horner said something about it not being possible with the wing spacers, but they don't stop you setting an angle of attack.

[McMacca]

I would have thought so, go to track, fastest corner is 220 kph, set AOA on wing to stall at 230 kph, ta da! reduced downforce/drag and higher top speed on straights where you reach over 230 kph. =D>

Yeah, fair enough. It's a bit confusing though because Horner said something about it not being possible with the wing spacers, but they don't stop you setting an angle of attack.

I think this is where the new wing comes into its own, in theory if fastest corner is 220 KPH you have to set your wing to stall at 220 +. But new wing stalls at 200 kph. Sounds crazy but then you add the extra airflow and suddenly the wing doesn't stall until 230 kph. UNLESS you cut the airflow (by closing a valve perhaps ) then it stalls 30 kph before your rivals.

Maybe

[volarchico]

The funny thing is that there is some engineer at McLaren reading this all right now, saying to himself either:

A) Ahh, they've finally got it.

or

B) Huh. That might just work.

+1

And I hope the drivers don't hit a bump wrong and activate this "knee" switch inadvertently in a high DF corner. Seems to be a dangerous way to activate something so important. I guess I'm still a skeptic.

[volarchico]

I think this is where the new wing comes into its own, in theory if fastest corner is 220 KPH you have to set your wing to stall at 220 +. But new wing stalls at 200 kph. Sounds crazy but then you add the extra airflow and suddenly the wing doesn't stall until 230 kph. UNLESS you cut the airflow (by closing a valve perhaps ) then it stalls 30 kph before your rivals.

Correct me if I'm wrong, but wings don't "stall" at a given speed. Their stall is caused by angle and that isn't changing. I understand the concept of the switch and the rest of the magic that's supposed to happen with the blown slot, but you can't create a wing to stall at a specific speed.

The blown flap can reduce stall and create attached flow where otherwise it would separate, so I could see how McLaren's switch could turn on the airflow to the slot to attach the flow and then turn it off to cause separation.

[McMacca]

I think this is where the new wing comes into its own, in theory if fastest corner is 220 KPH you have to set your wing to stall at 220 +. But new wing stalls at 200 kph. Sounds crazy but then you add the extra airflow and suddenly the wing doesn't stall until 230 kph. UNLESS you cut the airflow (by closing a valve perhaps ) then it stalls 30 kph before your rivals.

Correct me if I'm wrong, but wings don't "stall" at a given speed. Their stall is caused by angle and that isn't changing. I understand the concept of the switch and the rest of the magic that's supposed to happen with the blown slot, but you can't create a wing to stall at a specific speed.

The blown flap can reduce stall and create attached flow where otherwise it would separate, so I could see how McLaren's switch could turn on the airflow to the slot to attach the flow and then turn it off to cause separation.

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

Try it, Push the AOA and eventually the wing stalls, simples

[horse]

The blown flap can reduce stall and create attached flow where otherwise it would separate, so I could see how McLaren's switch could turn on the airflow to the slot to attach the flow and then turn it off to cause separation.

Yeah, this is the "always-on" concept, as opposed to blowing to cause the separation. We've been chatting about all these possibilities here. Still waiting for a good argument of how stalling reduces the drag, mind, as intuitively, it should do the reverse.

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

Try it, Push the AOA and eventually the wing stalls, simples

It stays stalled for all speeds though.

[newbie]

in as few words as possible:

F1 rear wing: highly cambered

high camber: downforce comes with severe induced drag penalty

closing rear-wing slot-gap or making it stall in any other way: downforce reduced

downforce reduced: drag reduced (significantly outweighing the drag penalty of a more lossy wake)

drag reduced: improved top speed

[volarchico]

well thats a blanket statement you persist in making without any explanation, diagram or anything other than I'm a Phd in Ground vehicle aerodynamics and work for an f1 team.

So until you actually explain yourself with science and not a belligerent attitude toward a counter intuitive concept I will consider you a fanboy with a fantasy.


Look forward to your side of the story.

I completely agree. I just finished reading through the McLaren thread and this thread after starting three days ago with the first post (yes I read them all...) and I came here today to specifically post exactly what you just said. I would love an explanation from SLC about how stalling the wing works to reduce the drag. Since he has his PhD and he's so confident in his solution, it should be no problem for him to teach it to someone else. I'm willing to learn, but I can't believe someone if they have no way to prove their opinion and aren't willing to try an explain themselves. I've had aircraft aeronautics pounded into my head for many years so perhaps that is my downfall in trying to understand this concept applied to an F1 car, so I'd really appreciate a lesson.

[WhiteBlue]

Story on McLaren rear wing slit debate

[horse]

in as few words as possible:

F1 rear wing: highly cambered

high camber: downforce comes with severe induced drag penalty

closing rear-wing slot-gap or making it stall in any other way: downforce reduced

downforce reduced: drag reduced (significantly outweighing the drag penalty of a more lossy wake)

drag reduced: improved top speed

Hmmm, interesting. So the detached flow has less drag than the attached flow. I assume the downforce must also be reduced, or you would run with the wing stalled all of the time. It's very hard to find information about multi-element wings in stall.

Are there any academic papers describing the process? I'd love to read them.

(yes I read them all...)

Wow, you must have the patience of a saint.

[volarchico]

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

Try it, Push the AOA and eventually the wing stalls, simples

Yeah, that's changing the angle of attack. In Formula 1, the angle of attack of the rear wing does not change appreciably during the race. Usually you cannot build a wing to stall at a specific speed for a specific corner and not stall at another speed. That's why the slot mentioned ad nauseum in this thread and the other is so interesting.

[McMacca]

The blown flap can reduce stall and create attached flow where otherwise it would separate, so I could see how McLaren's switch could turn on the airflow to the slot to attach the flow and then turn it off to cause separation.

Yeah, this is the "always-on" concept, as opposed to blowing to cause the separation. We've been chatting about all these possibilities here. Still waiting for a good argument of how stalling reduces the drag, mind, as intuitively, it should do the reverse.

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

Try it, Push the AOA and eventually the wing stalls, simples

It stays stalled for all speeds though.

Horse you are right, seems this model stalls any wing with an AOA of 10 degrees or more regardless of shape or speed!

NASA! Hmmmmph!

Obviously this cant be true or planes could take off at 10mph...... [-X

[volarchico]

Wow, you must have the patience of a saint.

Yeah, there were many times I wanted to ask a question, but then I'd look a few posts later and someone had already asked it, and then a few posts later someone had answered it. I read through it all to make sure I didn't repeat too much that has already been covered.