McLaren MP4-28 Mercedes

[tok-tokkie]

McLaren's Korea Updates Analyzed by GA

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via AutoSport

Is this the basic difference between those with the Coanda ramp taking the exhaust down to the floor (Red Bull, Sauber, Lotus) and those like McLaren, Ferrari & Mercedes where the Coanda ramp stops well above the floor?

Red Bull et al seal the side of the diffuser with exhaust gasses.

McLaren et al use the exhaust gasses to generate downforce directly on the wheel through the brake duct winglets and are not trying to really seal the diffuser. Problem with this interpretation is they have little vanes on the floor which look as if they are there to guide the exhaust plume between the tyre & diffuser edge..

[Crucial_Xtreme]

Is this the basic difference between those with the Coanda ramp taking the exhaust down to the floor (Red Bull, Sauber, Lotus) and those like McLaren, Ferrari & Mercedes where the Coanda ramp stops well above the floor?

Red Bull et al seal the side of the diffuser with exhaust gasses.

McLaren et al use the exhaust gasses to generate downforce directly on the wheel through the brake duct winglets and are not trying to really seal the diffuser. Problem with this interpretation is they have little vanes on the floor which look as if they are there to guide the exhaust plume between the tyre & diffuser edge..

I think Gary Anderson is off his rocker saying that teams(Ferrari/McLaren?etc) are using the exhaust for only the brake ducts. Ferrari, McLaren etc are also trying to seal the diffuser with their exhaust, they're just doing it without the ramp.

[horse]

Given the distance between exhaust and floor, I would very much doubt if you could "direct" the entire exhaust flume either the diffuser or the brake ducts. Some proportion will go to the floor, some around the wheel.

It could simply be that McLaren can't achieve more with the floor using their exhaust system and that they are looking to gain more from the brake ducts.

[Crucial_Xtreme]

Given the distance between exhaust and floor, I would very much doubt if you could "direct" the entire exhaust flume either the diffuser or the brake ducts. Some proportion will go to the floor, some around the wheel.

It could simply be that McLaren can't achieve more with the floor using their exhaust system and that they are looking to gain more from the brake ducts.

I agree the exhaust doesn't use only one or the other, but GA has opined since early last season that teams, even RB with their ramp were targeting exhaust gasses at the rear brake ducts, and still says it to this day. He's simply wrong.

Pre-Season Testing 2012
2013

He has it stuck in his mind that teams are only trying to blow brake ducts as you can see in 2nd image.

[turbof1]

Given the distance between exhaust and floor, I would very much doubt if you could "direct" the entire exhaust flume either the diffuser or the brake ducts. Some proportion will go to the floor, some around the wheel.

It could simply be that McLaren can't achieve more with the floor using their exhaust system and that they are looking to gain more from the brake ducts.

I agree the exhaust doesn't use only one or the other, but GA has opined since early last season that teams, even RB with their ramp were targeting exhaust gasses at the rear brake ducts, and still says it to this day. He's simply wrong.

Pre-Season Testing 2012
2013

He has it stuck in his mind that teams are only trying to blow brake ducts as you can see in 2nd image.

I often like a different opinion. Gives a fresh look on things. However, in the Gary Anderson 'nut'-case, BBC is better off screening this forum for a potentional replacement. He very often makes statements which make no sence at all.

Teams don't explicitly target the brake ducts. Although in theory gives a big downforce gain, it is much too sensitive. Instead, they try to replicate what they have been doing since 2011: seal the diffuser, have a bigger rake, have more downforce.

He atleast kept a bit of an open mind back in 2012 pre season, telling "brake duct or floor".

[Kiril Varbanov]

He's simply wrong.
...
He has it stuck in his mind that teams are only trying to blow brake ducts as you can see in 2nd image.

Which reminds me of myself when I was starting couple of years ago trying to decode what the teams were doing - I had certain ideas stuck into my mind, and they were the base for all other thoughts. Hence, I was wrong from the very beginning. The good thing is that I haven't had the lavish opportunity to send my erroneous mindset to the world.

Back on Gary Andrerson's thoughts, again, my full respect to a former technical director of a Formula 1 team. I'd love to talk to him in person, but to be fair, the BBC guys are superstars, and I'm not even going to try.

On this particular occasion, I'd set my ramblings on the commonly accepted theory (proven in thousands of races) that the teams are trying to seal the trailing edge of the diffuser, hence creating a low pressure zone, further supplemented by the accelerated flow underneath. Aero books are also saying (as well as certain top F1 team designer) that we also need to take into account the lateral channels counter-rotating vortices, whose strength and management can give you nice peak performance.

Essentially, the exhaust gases going on the sides of the diffuser have two outcomes:
- to strengthen the side-edge vortices inside the diffuser
- to act as air curtains, preventing the ingress of turbulent air created by the rotating rear wheels.

The brake ducts idea would be a massively sensitive matter and a source for tire overheat.

Back on Mclaren, as already pointed out, small changes in the front wing configuration, and I think there's one less stiffener.

[monsi]

Here's where I show up my lack of detailed technical knowledge, but why would the exhausts be the source of the air that can act on those wing shaped brake ducts. Why not design these ducts so that the main rush of air is what provides the downforce direct to the wheels ? Would any contribution from the exhausts not be both smaller and more variable to boot ? i.e. a nice extra but not the main reason.

[turbof1]

Here's where I show up my lack of detailed technical knowledge, but why would the exhausts be the source of the air that can act on those wing shaped brake ducts. Why not design these ducts so that the main rush of air is what provides the downforce direct to the wheels ? Would any contribution from the exhausts not be both smaller and more variable to boot ? i.e. a nice extra but not the main reason.

The brake duct always are designed to create downforce from normal airflow. What exhaust gasses would do is energise that airflow, accelerating it, which creates more downforce. You are not replacing one with the other, they are complementary.

[shelly]

Short aspect ratio wings like brake duct winglets are a specific category of wings (called A-wings, iirc). they produce downforce like a delta wing, riding their own tip vortices. So, if one wanted to maximise downforce on brake ducts with exhausts, the jet should be aimed ont over the center of the winglets, but at the edge of them, were the tip vortex stays.

But I think ther is much more to gain in blowing the footplate vortex on the sied edge of the diffuser.
In the 80s-90s exhaust blowing was mainly about momentum -i.e. increasing the momentum of the flow in the diffuser; in these years it seems the main effect that is about angular momentum - i.e. accelerating vortices to get increased helicity

[trinidefender]

Short aspect ratio wings like brake duct winglets are a specific category of wings (called A-wings, iirc). they produce downforce like a delta wing, riding their own tip vortices. So, if one wanted to maximise downforce on brake ducts with exhausts, the jet should be aimed ont over the center of the winglets, but at the edge of them, were the tip vortex stays.

But I think ther is much more to gain in blowing the footplate vortex on the sied edge of the diffuser.
In the 80s-90s exhaust blowing was mainly about momentum -i.e. increasing the momentum of the flow in the diffuser; in these years it seems the main effect that is about angular momentum - i.e. accelerating vortices to get increased helicity

Shelly for those types of wings to work then they actually have to be delta wings. They have to have an inward angle as they go toward the front (a large sweep angle) so that the the vortex, caused by air from the high pressure side spilling over onto the comparatively low pressure side, keeps airflow attached at high angles of attack. These wings tend to have vortices over a large portion of the wing. I think that McLaren are trying to run them as traditional wings. The reason I say this is because of the large vertical surface on the edge of the brake ducts. This large vertical section reduces vortices by a large amount and cuts drag. If you want an example look at the end plates on the rear wing. Or in aviation many modern commercial aircraft have them. Boeing calls the winglets, Airbus calls their version wingtip fences/sharklets.

While blowing the diffuser might be a better way to do things maybe McLaren are having trouble getting all of their exhaust flow to the floor. Well if they can't figure out a way to get ALL to the floor then why not try to make the best of the exhaust plume that isn't at floor level. Put these fenced in brake duct wings to create downforce with the high energy exhaust plume that is there.

Another thing to note. By creating downforce directly on the wheel then you can run slightly more compliant suspension as it has to deal with less downforce as it has been moved directly to the wheels, in turn helping low speed cornering.

[shelly]

I agree with you about endplates: then I think we have to look at the lower edge of the endplate of the brake ducts, where the assembly vortex detaches. The piola sketch seem to shw that this vortex interacts with the rw lower endplate vortex. The same sketch posted above shows that the lower surfaces are without endplates ->vortices. I would like to see some more pictures, though,before saying something too wrong.
If I am not mistaken, rbr and ferrari also run twosted brake duct winglets: when I see abrupt aoa changes I always thing that there is a vortex passing through them and the twist is needed to adapt the aoa locally. I will try to dig some photos

[raymondu999]

[dren]

Given the distance between exhaust and floor, I would very much doubt if you could "direct" the entire exhaust flume either the diffuser or the brake ducts. Some proportion will go to the floor, some around the wheel.

It could simply be that McLaren can't achieve more with the floor using their exhaust system and that they are looking to gain more from the brake ducts.

I agree the exhaust doesn't use only one or the other, but GA has opined since early last season that teams, even RB with their ramp were targeting exhaust gasses at the rear brake ducts, and still says it to this day. He's simply wrong.

Pre-Season Testing 2012
2013

He has it stuck in his mind that teams are only trying to blow brake ducts as you can see in 2nd image.

Surely he can see the rather large cut outs in the floor edge by the tires, the strakes on the floor top, and the pieces on the bottom of the brake duct/wing combo that help seal off that area. That, and just follow the coanda and where is the gas going...on the freaking floor!

[shelly]

@trinidefender: short span wings do not need to be delta to ride vortices - the name I was looking for is Zimmerman wings. Lots of precious info here:
http://www.acsol.net/~nmasters/vortex-lift/

[MGRM]

http://www.youtube.com/watch?v=RaW-jaJu ... tu.be&hd=1