Reducing the drag of a two element wing through stall

[modbaraban]

edit: does anyone have a CFD image to illustrate what actually aerodynamic stall is? (no need to explain, I've read the wiki once, but I'd like to see it)

[rkn]

This illustrates wing stall, (the lower one)

[SoundMan]

I think you would want any wings to stall at a certain speed, since the less wing on the straights the better.

i'm fairly sure that you dont want full wing stall along the straights because this will cause even greater drag. you are correct that you obviously want less aerodynamic downforce (ie by using less wing) because this gives less drag in the straights, but you wouldnt want to decrease downforce by simply having the wing stall because this, i would suggest, increases drag greatly - over and above the normal wing producing downforce with mostly laminar flow.

but hell, i dont know for sure, so would love to know for certain...

[Ogami musashi]

No you're right, the term "stall" is incorrect.

The practice related to a change in the angle of attack of the wing so that the drag coefficient is better.

The illustrations of a stall are actually quite misleading too, they suggest the air go away from the wing which is not the case, a "stall" is when flow's vector are reversed and eventually become random in motion, but even totally stalled, a wing stays with flow's attached on her, this is the pressure (due to differences in momentum) repartitions that changes.

[Gecko]

Ogami, the picture is quite correct, the flow lines do detach from the wing on the top side, but the volume between the top and bottom (average) streamlines is filled with random turbulent motion. It is correct that there is no "hole" in the flow as the fluid density is everywhere almost constant, but the streamlines do detach from the surface.

[Sikthskies]

I was talking to a guy from McLaren last week and I was asking him about the car (naturally) and we got onto the engine cover/fin and he said 'I can't say anything about it apart from it's not what it is, it's what it does'.

What could that possibly mean? i heard another guy saying that this 'feature' hasn't yet worked during testing (that was tuesday)

Any ideas?

[segedunum]

Your guess is as good as anyone's. Check out the extremely long MP4/25 thread:

viewtopic.php?f=12&t=7495

There's everything from new aerodynamic concepts like dead zones to some extremely thinly veiled hints that various people won't explain fully. One thing's for certain is that whatever it is, McLaren have yet to find it out on the track.............

[Callum]

Goony??

[manchild]

It vibrates (flexes) laterally at high frequency, acting as fan that directs more air on the rear wing than it would naturally get there.

It is based on an old sculling technique used mainly for survival, when there is only one oar at disposal, and person can't use both hands due to injury.

Oar is placed longitudinally at the back of the boat, the way outboards are, and moved slightly left to right (and back) without being pulled out of the water.

Almost identical to this:


http://www.diy-wood-boat.com/Sculling.html

[DaveW]

It vibrates (flexes) laterally at high frequency, acting as fan that directs more air on the rear wing than it would naturally get there.

It is based on an old sculling technique used mainly for survival, when there is only one oar at disposal, and person can't use both hands due to injury.

MacLaren Aerodynamicist: "Duh. No wonder it doesn't work. We forgot the lanyard." (with apologies).

More seriously, the single scull technique works because the oarsman supplies energy. Where is the energy source for the "sharks fin"? The most obvious would be the airflow, I suppose (think flying flag), but that probably wouldn't improve the efficiency of the rear wing.

For what it's worth, I suspect the main function of the sharks fin is to recover weathercock stability, which must have taken a hit following the recent forward shift of the centre of pressure. Its potential effectiveness would be reduced by the rear wing end plates, one might think.

[manchild]

I wrote "Almost identical to this:" since there was no better pic. Lanyard is used in traditional Chinese sculling, not in Western, but the principle is the same.

Energy source = vibrations coming from the engine.

[Richard]

Manchild

I would have thought your suggestion would need the fin to flex and resonate . However, the McL fin has a lot of cross section depth compared to a conventional flat plate. So would it be be too stiff for your suggestion?

Possibly the way it is tapered could lead to a suggestion that it is tuned to avoid resonance?

[Giblet]

Goony??

Nah too much punctuation, capitalization, and breaks in sentences.

I like Goony, but his paragraphs were a little, um, rudimentary.

[Richard]

Goony??

Nah too much punctuation, capitalization, and breaks in sentences.

I like Goony, but his paragraphs were a little, um, rudimentary.

A bit like the title of this thread?

[manchild]

Perhaps it transmits heat to rear wing, allowing it to flex more than reg. permit while the engine is running? It could be done easily in many ways. By the time cars stalls in Parc Ferme, it would cool off making wing less flexible again before scrutinizing begins?