Mclaren Mercedes MP4-25

[Raptor22]

It is definitely a stalling mechanism. Yes, this will decrease the effectiveness of the diffuser but at 300kph down a straight you don't really care about the absolute downforce level you are producing - as long as you can shed 10-15 pts of Cd.

And yes, it is driver operated. Somehow.

You're free to believe this, just like some people believe in the 2nd coming.

However, you have to appreciate that the rear wing and diffusor work in conjunction with each other.
Higher efficiency of the rear wing increase the scavenging of the diffusor which increase downforce.
remove the rear wing and the diffusor alone does not keep the car on the ground nor does it maintain stability. If it did then when a rear wing falls off, the car would go faster and still be stable. However we see in reality that when a rear wing falls off, the car looses stability.
If you stall the rear wing, its the same effect as removing the wing.

Maintaining equal pressure on both upper and lower surfaces of the wing is not possible unless you can blow a very large VOLUME of air into the wake behind the wing. You cannot achieve that without a large pump pumping slowly. So the only way to stall the wing is too use the engine as a pump, robbing power.

The purpose of the flap blowing has nothing to do with stall. get over it, its science fiction.
Flap blowing is about wing efficiency through boundary layer control.

i know we love to get the creative juices flowing so lets talk about magnetic levitation for the MP4/25 or how about turning it into a hover craft down the straight with all the stalled air in the now choked (if you believe in wing stall) diffusor. Lets discuss some stability control mechanisms to make this work.

Stalled wings is nonsense, can we move on...

[imightbewrong]

This is what scarbs thinks it is:
http://scarbsf1.wordpress.com/2010/02/1 ... shark-fin/

Apparently the idea was taken from BMW:
http://scarbsf1.wordpress.com/2010/02/1 ... apan-2009/

[Raptor22]

The only way to reduce the lift is to change the angle of attack of the wing to the air flow.
Maximum downforce requires highest possible AoA without flow separation. Flap blowing achieves this by filling in air where flow separation occurs for a given wing. Its the flow separation that creates turbulent dragging flow that eventually becomes stall if the AoA is too high for the foil section.

The way they achieve this in F1 wings is to use a foil section of high chord depth, which creates a lovely hollow inside the wing with the space that results.

Wth flap blowing, a huge pressure difference is not needed, you just need to maintain it slightly above atmospheric and the low pressure behind (or on top in a normal aircraft wing) creates the gradient for air to flow out of the wing since it is open to atmposhere.

Also stalling the wing will reduce the effectiveness of the diffusor. Through stalling the fall, they will choke the diffusor which is NOT what anybod wants because the car will become unstable.

There is no stall going on here, the flap blowing is there to increase the effectiveness of the wing.
How top speed will be affected is that a more efficient wing will create similar downforce for a smaller angle of attack. The lower angle of attack has a smaller wake and less drag.

I dont totally agree - a component on its own most likely true, but rear wing with diffuser isnt totally true...infact your wrong...dunno about macca flow vis, but trust me downforce isnt always about getting everything to work in PERFECT conditions...

The rear wing can produce sufficient downforce without a diffusor.
A diffusor under the current regulations cannot produce enough downforce without a rear wing.
Example, what happens when the rear wing falls off?

once you have answered that for yourself then it will lead you down a path of component integration and how these components interact.

If we could build ground effect cars then the underbody would be the greatest downforce producing component. But we can't. We stepped bottom cars where the only viable underbody downforce generating devices performance is measured by how efficiently it can extract air from under the car so that the wings can force the car down while creating less drag. Yin and Yang, wing and diffusor.

[horse]

Those pics clearly show attached flow. Show me the stall...

Can we talk a bit about the flow-viz, Raptor? What do you think is happening on the flap element? My take on it was that the slot or ridge was causing some eddy to be formed there, hence the collecting of paint, yet it does appear as if the flow is well attached again at the trailing edge of the foil element. I thought perhaps there might be some sign of reversal at the top of the element although that could just be dripping. Here's bar555's big picture again (see the middle one):

[bar555]

That rear wing study is not the only think to focus on , i agree it is a novelty but there are many other interesting parts of the car to discuss about , for instance the hot air exits and pitot rakes .


A variety of Pitot rakes were used during the test at Jerez to help the team evaluate the air speed not only around the car but also the speed of air entering into the radiators inlets .




It is no secret that the new MP4/25 faces overheating problems . The sidepods are really very compact , even with the new much larger fuel cell and there are many different types of hot air exiting holes around the car body to cool the car . There are long slits at the front upper sidepods part (1) , at cockpit sides like the Red Bull RB5 and at the rear . So the team need to measure the air speed entering the sidepod inlets - radiators to find out if the cooling needs are fullfilled or not .

[horse]

A variety of Pitot rakes were used during the test at Jerez to help the team evaluate the air speed not only around the car but also the speed of air entering into the radiators inlets .

Thanks bar555, another great collection of pics.

I think there was some concenus that the long adjustable rake was to aid understanding of the flow about the new, thinner tyres and this obviously has impact on the radiator inlets. I also thought it may be to assess the performance of the new nose cone splitter that they have adopted.

To be honest, I wasn't aware (or hadn't realised) that they were having overheating problems.

[bonjon1979]

A variety of Pitot rakes were used during the test at Jerez to help the team evaluate the air speed not only around the car but also the speed of air entering into the radiators inlets .

Thanks bar555, another great collection of pics.

I think there was some concenus that the long adjustable rake was to aid understanding of the flow about the new, thinner tyres and this obviously has impact on the radiator inlets. I also thought it may be to assess the performance of the new nose cone splitter that they have adopted.

To be honest, I wasn't aware (or hadn't realised) that they were having overheating problems.

They haven't. A German site reported that they may have overheating problems after seeing the slots on top of the sidepod appearing during the very first test. They assumed it had something to do with overheating issues. None have been actually confirmed and there's been no reports of it after their long runs.

[Raptor22]

Those pics clearly show attached flow. Show me the stall...

Can we talk a bit about the flow-viz, Raptor? What do you think is happening on the flap element? My take on it was that the slot or ridge was causing some eddy to be formed there, hence the collecting of paint, yet it does appear as if the flow is well attached again at the trailing edge of the foil element. I thought perhaps there might be some sign of reversal at the top of the element although that could just be dripping. Here's bar555's big picture again (see the middle one):

HOrse,

When air lfow leaves a wing it reverts to atmospheric pressure. What I think we are seeing is typical of a denser fluid medium being deposited on the trailing edge of the wing as it leaves the wing surface.
this is probably a function of the surface tension of the liquid fluid and the air density and pressure interaction that occurs here.

An example would be the trailing edge of a wing in flight during rain. Water always collects at the trailing edge and leaves in large droplets. Even in mist you will find the trailing edge gathers droplets of water. there is a phase change here with the change in density, that creates a little turbulent flow that re deposits the paint on the trailing edge. The flow back of Flow Vis Paint we see at the upper element trailing edge is merely that I believe. the lines are certainly consistent with dripping wet paint. If you have a model airplane, mix up some water based paint and pread it out on the wing. Now take the plane for a short flight and land. Have a look at the trailing edge. there shuld be a thick line of paint right at the edge.


I would like to see under the engine cover of the MP4/25 whether they have merely build a sealed sction above the airbox or if there is a chamber.
Thinking about it from a mechanic friendly perspective I would think that the flap blowing plumbing would be part of the engine cover an that theres a sealing ring build around the airbox to

[Just_a_fan]

It is no secret that the new MP4/25 faces overheating problems . The sidepods are really very compact , even with the new much larger fuel cell and there are many different types of hot air exiting holes around the car body to cool the car . There are long slits at the front upper sidepods part

I've been thinking about those slots. I wonder if they are more to do with the quality of air flow over the top of the sidepod. At higher speeds, air will be hitting the front of the sidepod opening at a rate that may exceed the ability of the rad cores and sidepod exhausts holes to flow the air. This would cause turbulent air to spill out of the front of the sidepod (it would choke, effectively). Putting in these slots allows the air to bleed out of the volume in front of the rad cores in a controlled way so maintaining flow quality over the top of the sidepods. This helps reduce drag caused by the oversill as well as improving air quality to the rear end of the car.

The location and shape of them certainly suggests they are there to exhaust air rather than let it in.

Of course, helping to unchoke the sidepod inlet would probably have a beneficial effect on cooling performance too.

I think the under nose splitter device is designed to help cooling flow too by creating a vortex that runs along the lower edge of the nose/chassis and in to the sidepod openings. I remember photos of the MP4-24 with flow viz in the area of the sidepod entry showing a clean air path to the opening from the front end of the car. I wonder if this is a more evolved solution to ensuring decent quality air entering the sidepods and so reducing drag from 'overspill'.

The splitter may be there to improve airflow off the front wing and towards the undertray though (this is more likely in my mind too)

[zgred]

[Raptor22]

the undernose splitter would certainly be present to increase front end downforce.
Have not seen opics that shows the flwo from here to the radiator inlet but what you say is entirely plausible.

De-Choking the inlet is also a strong possibility of purpose for the sidepod vents at the front. Whether it improves the airflow down the side pod is debatable becauseit will result in mixing and therefore turbulent flow down the side pod to the rearof the car and over the lower rear wing.
Now that wing could be seing turbulent flow over its top anyway so maybe its not a problem
It could be the reason for the integrated lower rear wing and diffusor upperdeck.

Again have not seen much pictorial evidence to suggest whats happening in that area.

[horse]

When air flow leaves a wing it reverts to atmospheric pressure. What I think we are seeing is typical of a denser fluid medium being deposited on the trailing edge of the wing as it leaves the wing surface.
this is probably a function of the surface tension of the liquid fluid and the air density and pressure interaction that occurs here.

Ah, right, I think I have witnessed that before, yes, thanks. Are you saying this is happening at both the trailing edge and the slot or just the trailing edge? I suppose I'm pushing for whether you think the flow-viz supports a blown flap there?

Also, what's with the red flow-viz? Do they think we're being too nosey, or did they just run out of green? It'll be hard to make out on a red wing anyway.

That diffuser outlet is enormous, isn't it?

[bar555]

They haven't. A German site reported that they may have overheating problems after seeing the slots on top of the sidepod appearing during the very first test. They assumed it had something to do with overheating issues. None have been actually confirmed and there's been no reports of it after their long runs.

Permit me to have a different opinion . It is not the total number of the exits around the car body but the fact that the team has been changing them all the time , testing different cooling options. Judge for yourself .









That would not happen if the cooling systems of the car were working properly

[TheMinister]

It is definitely a stalling mechanism. Yes, this will decrease the effectiveness of the diffuser but at 300kph down a straight you don't really care about the absolute downforce level you are producing - as long as you can shed 10-15 pts of Cd.

And yes, it is driver operated. Somehow.

Here's a question- does the total drag of the wing/car decrease once the wing stalls?

(if it does then....)

It seems to me that if blowing air through the flap tends to delay the speed at which the trailing edge of the wing stalls, the team can then actively control when the wing is stalled.

If the system is purely passive then this will have to be set for each track; ie China you will want less drag down the long straight, so stall it earlier, whereas Silverstone with long fast turns will want more high speed downforce so stall it later.

The possibilities are even more exciting if the team can actively control the flow of air while driving; down any straight they could stall the wing, whilst still keeping it going in high speed turns.

As usual though, it's conjecture and probably banned ideas from me... oh well....

[kalinka]

It is definitely a stalling mechanism. Yes, this will decrease the effectiveness of the diffuser but at 300kph down a straight you don't really care about the absolute downforce level you are producing - as long as you can shed 10-15 pts of Cd.

And yes, it is driver operated. Somehow.

Here's a question- does the total drag of the wing/car decrease once the wing stalls?

(if it does then....)

It seems to me that if blowing air through the flap tends to delay the speed at which the trailing edge of the wing stalls, the team can then actively control when the wing is stalled.

If the system is purely passive then this will have to be set for each track; ie China you will want less drag down the long straight, so stall it earlier, whereas Silverstone with long fast turns will want more high speed downforce so stall it later.

The possibilities are even more exciting if the team can actively control the flow of air while driving; down any straight they could stall the wing, whilst still keeping it going in high speed turns.

As usual though, it's conjecture and probably banned ideas from me... oh well....

I posted before a clear research paper on this. Obviously not seen by lot of people here. Though it's an old paper back in 1964, but it's some kind of a US military research result on blown wings. So here it is again :

http://oai.dtic.mil/oai/oai?&verb=getRe ... =AD0603904

The most important detail in it I think :

"Lift coefficient increased appreciably with blowing at low values of the parameters, and then tended to level off as blowing was increased. At low angles of attack, the only additional drag induced by blowing was the momentum drag due to the rearward thrust of the jets. It was found that such blowing reduced the stability of the wing. "

From this we can assume that is no need for high velocity airflow to create the blow effect, thus the air intake above driver's helmet would be enough. Another thing : it seems the effect is leveling with increasing speed,so in long straigts there would be no additional downforce with/without blown wing. And it's good for us !!!

Of course under "lift coefficient" we must replace with "downforce coefficient" in our case.