Mclaren Mercedes MP4-25

[De Jokke]

Impressive beast, the 25, hope it runs reliable tomorrow and proves to be fast the coming days! [-o<

Tomorrow basic checks with paffet, hope he doesn't drive the thing into a wall

I wonder if we're going to see flowvis again...

[Pup]

I will say that the fin obviously (ominously?) has some dimension to it. There's room for a duct, albeit a small one...

http://www.gurneyflap.com/Resources/MC04.jpg

If there's no duct, then I'm at a loss to explain the thickness.

[ringo]

The fin putting air on the wing wont be of much help. The air wont be a better quality of the free stream air. Stalling is also not desirable at any rate, the wing would behave like a bluff body only creating drag.
The air through the heat exchangers is not steady either and it loses most of the KE hitting into the grating of the exchangers.

What could work however, is if air was injected behind the wing, between the wing elments though a duct in the fin. This air would have to be at a higher pressure than that on the low pressure side of the wing. Introducing high pressure behind the wing would reduce the pressure difference between the sides of the wing, reducing drag and reducing lift. This only works if the enthalpy gained by the air going through the heat exchangers can restore most of the pressure and energy lost.
For it to work the injected pressure has to be higher than that behind the wing. the closer it is to free stream pressure the better. With equal pressure on both sides, ideally the wing would behave as if it was not there, no drag and no down-force.

Something like this:


The curved lines are the wing, red lines hot air, blue low pressure and free stream.
The drawing is a not dimensionally accurate, but you all should get the idea.

This reduction in drag and down-force thing is only desirable on the straights, when a DF reduction wont hurt.

[Shrek]

The fin putting air on the wing wont be of much help. The air wont be a better quality of the free stream air. Stalling is also not desirable at any rate, the wing would behave like a bluff body only creating drag.
The air through the heat exchangers is not steady either and it loses most of the KE hitting into the grating of the exchangers.

What could work however, is if air was injected behind the wing, between the wing elments though a duct in the fin. This air would have to be at a higher pressure than that on the low pressure side of the wing. Introducing high pressure behind the wing would reduce the pressure difference between the sides of the wing, reducing drag and reducing lift. This only works if the enthalpy gained by the air going through the heat exchangers can restore most of the pressure and energy lost.
For it to work the injected pressure has to be higher than that behind the wing. the closer it is to free stream pressure the better. With equal pressure on both sides, ideally the wing would behave as if it was not there, no drag and no down-force.

Something like this:


The curved lines are the wing, red lines hot air, blue low pressure and free stream.
The drawing is a not dimensionally accurate, but you all should get the idea.

This reduction in drag and down-force thing is only desirable on the straights, when a DF reduction wont hurt.

What about the suction that air creates when flowing over a tube(I think), would that help the situation?

[CHT]

http://www.youtube.com/watch?v=jSLA_2J7QYg

There is a good view of the fin at 1:58sec

[Pup]

Something like this:


The curved lines are the wing, red lines hot air, blue low pressure and free stream.
The drawing is a not dimensionally accurate, but you all should get the idea.

This reduction in drag and down-force thing is only desirable on the straights, when a DF reduction wont hurt.

I think you've described it perfectly. The only thing I would change is that the duct would probably come from the topmost section of the intake, since it has a straight shot and would be in the best airflow. I'd also add back in the idea of a hollow, pressurized rear wing, which could be slotted to allow an even release of air.

But the questions remain - A) could enough air be shot to the back of the wing to make any real difference?, and B) how can this system be made to turn on and off when desired?

[ringo]

The fin putting air on the wing wont be of much help. The air wont be a better quality of the free stream air. Stalling is also not desirable at any rate, the wing would behave like a bluff body only creating drag.
The air through the heat exchangers is not steady either and it loses most of the KE hitting into the grating of the exchangers.

What could work however, is if air was injected behind the wing, between the wing elments though a duct in the fin. This air would have to be at a higher pressure than that on the low pressure side of the wing. Introducing high pressure behind the wing would reduce the pressure difference between the sides of the wing, reducing drag and reducing lift. This only works if the enthalpy gained by the air going through the heat exchangers can restore most of the pressure and energy lost.
For it to work the injected pressure has to be higher than that behind the wing. the closer it is to free stream pressure the better. With equal pressure on both sides, ideally the wing would behave as if it was not there, no drag and no down-force.

Something like this:


The curved lines are the wing, red lines hot air, blue low pressure and free stream.
The drawing is a not dimensionally accurate, but you all should get the idea.

This reduction in drag and down-force thing is only desirable on the straights, when a DF reduction wont hurt.

What about the suction that air creates when flowing over a tube(I think), would that help the situation?

It depends on the pressure difference between the inside and outside of the tube. In this case there will be a suction for sure if the outside is at a lower pressure.
For all we know there could be a little butterfly valve in there somewhere and it might be perfectly legal because these aero devices are underneath the skin of the car. I am not sure if aero regs cover anything but what is affixed to the outer body.
The valve is shut in the corners and open on the straights when the DF is not needed. This is all conjecture by the way.

[ringo]

I think you've described it perfectly. The only thing I would change is that the duct would probably come from the topmost section of the intake, since it has a straight shot and would be in the best airflow. I'd also add back in the idea of a hollow, pressurized rear wing, which could be slotted to allow an even release of air.

But the questions remain - A) could enough air be shot to the back of the wing to make any real difference?, and B) how can this system be made to turn on and off when desired?

Now that i saw the video it could definitely come from the top section.
About your questions,
A. i suppose it could make a slight difference, I wish i knew more about cross flows and 3d flow.

B. A butterfly valve in the fin, manually operated by the driver.

[conni]

my thoughts are that an engine can only use SO much air the rest builds up infront of the airbox and spills over the sides and over the wing so if at a certain pressure inside the airbox a valve opend and allowed the excess air to go straight through this would cut down on the amount going over the wing maybe?
and as the fin is taperd the air will speed up passing through it and if you had a slot or holes in the side of the fin maybe you would get a venturi effect and suck air in from outside in effect creating a deadzone a vacume and no air going over the wing all of this assumes that the engine doesnt use all of the air available and youd need a lot left over to make it work

conni

[gibells]

my thoughts are that an engine can only use SO much air the rest builds up infront of the airbox and spills over the sides and over the wing so if at a certain pressure inside the airbox a valve opend and allowed the excess air to go straight through this would cut down on the amount going over the wing maybe?
and as the fin is taperd the air will speed up passing through it and if you had a slot or holes in the side of the fin maybe you would get a venturi effect and suck air in from outside in effect creating a deadzone a vacume and no air going over the wing all of this assumes that the engine doesnt use all of the air available and youd need a lot left over to make it work

conni

bingo. now i get it. thanks mate.

[djones]

I've only just realised the fin actually connects to the rear wing. I thought it stopped just short!

[tarzoon]

my thoughts are that an engine can only use SO much air the rest builds up infront of the airbox and spills over the sides and over the wing so if at a certain pressure inside the airbox a valve opend and allowed the excess air to go straight through this would cut down on the amount going over the wing maybe?
and as the fin is taperd the air will speed up passing through it and if you had a slot or holes in the side of the fin maybe you would get a venturi effect and suck air in from outside in effect creating a deadzone a vacume and no air going over the wing all of this assumes that the engine doesnt use all of the air available and youd need a lot left over to make it work

conni

Looks like you've been giving it quite a bit of thought. =D> =D>

One question: is it a good thing having a larger airbox to create directed flow?

[imightbewrong]

[Raptor22]

Definately on the right track but not convinced that the air simply spills out of an orrifice and fills in a vacuum (low pressure area).

There is more to be gained by speeding up air flow under the wing reducing the pressure there further.

I can;t see how stall can be induced without mechanical intervention and that is very clealy illegal.

The bulbous area just behind the airbox is likely a pressure chamber feeding a stream of air at low pressure to the lowe pressure area of the rear wing, speeding up the flow in that area and lowering the pressure.

By keeoping that flow energised it remains coupled to the wing elements reducing the induced drag on the wings, olowering drag without sacrifising downforce.

I don;t believe the ruls state that a wing has to be uniformly closed since openings are required in the area where it fixes to the endplates, upright support etc. through interpretation these can be exploited especially if the fin is part of the primary support structure.

[myurr]

Are they using the entire volume under the bridge wing? Great shot but it's still really hard to tell what's going on in there. Whatever they're doing it looks complicated!