2012 Exhaust Blowing & Coanda

[shelly]

@smikle: have you tried with zero or near ero wind speed? Coanda effect should be there when the caris stationary also (downwash and inwash not into play).
How strong is the sucion peak form the diffuser? If tha diffusr is working, it should draw tha plume down and to the inside slightly across the footplate

[bonjon1979]

I wish to research what happens to the exhaust plume when it enters the atmosphere. What thermodynamic or aerodynamic word descriptions could be used to describe this activity? Using simple descriptions is getting me nothing.

Brian

When an exhaust jet exits into a cross-stream, the jet almost behaves like a deformable solid.


Search for this paper--> Aerodynamic effectiveness of the flow of exhaust gases in a generic formula one car configuration

by F.L.Parra and K.Kontis in 2006

The very nature of that implies energy loss too. So you could argue that this type of exhuast has a compromise VS The exhaust that shoots straight backwards as seen on the RedBull. Of course it as all about how much is sacrificed to get the exhuast where you want it. Maybe Newey rather high energy in a not so fancy location VS low energy in a fancy location.

Awesome work.

[OO7]

Here are my little CFD tests on the Mclaren MP4-27 exhaust as promised.

Excellent work n smikle, thank you =D>
It looks like the exhaust gases are blowing the outer diffuser and floor as last year, as well as the brake duct fins and tyres (depending on speed). It looks like McLaren may have gone for the trifecta here .

[PlatinumZealot]

@smikle: have you tried with zero or near ero wind speed? Coanda effect should be there when the caris stationary also (downwash and inwash not into play).
How strong is the sucion peak form the diffuser? If tha diffusr is working, it should draw tha plume down and to the inside slightly across the footplate

I was not testing the diffuser, so I did not take time to draw it right, the throat was just an ugly step instead of a smooth transition.

[CountessBathory]

@n smikle, awesome job.

Btw, would you be so kind as to show us some pics of the meshes?

Thanks in advance.

[shelly]

@smikle: have you tried with zero or near ero wind speed? Coanda effect should be there when the caris stationary also (downwash and inwash not into play).
How strong is the sucion peak form the diffuser? If tha diffusr is working, it should draw tha plume down and to the inside slightly across the footplate

I was not testing the diffuser, so I did not take time to draw it right, the throat was just an ugly step instead of a smooth transition.

A working diffuser will suck in the exhausts probably, it has a very strong downwash near th footplate. What about zero speed Are you trying it?

[AbulafiaF1]

@n smikle: Fascinating CFD results there mate, kudos... =D>

I was wondering if you are planning on providing more CFD analysis for Mercedes, Red Bull and Ferrari, in particular. I presume that Ferrari have a similar concept to McLaren, but Red Bull and Mercedes have (so far) used more conservative designs. With regards to Mercedes in particular, it would be nice to see if they are trying to blow the added slot on the diffuser, below the rear light. Any plans?

Thanks again for this...

[Kiril Varbanov]

With regards to Mercedes in particular, it would be nice to see if they are trying to blow the added slot on the diffuser, below the rear light. Any plans?

They should be, otherwise I don't see the reason for the extra slot there.

[ringo]

@smikle: have you tried with zero or near ero wind speed? Coanda effect should be there when the caris stationary also (downwash and inwash not into play).
How strong is the sucion peak form the diffuser? If tha diffusr is working, it should draw tha plume down and to the inside slightly across the footplate

I was not testing the diffuser, so I did not take time to draw it right, the throat was just an ugly step instead of a smooth transition.

A working diffuser will suck in the exhausts probably, it has a very strong downwash near th footplate. What about zero speed Are you trying it?

no it wont. There are some examples showing air coming from the sides with tunneled floors, but the F1 floor is different.

After the throat there is no inward tendency for air flow.
What you will find also is that the upwash from the brake duct airfoils will influence the exhaust to go upward as well.

But to get back to mclaren, i think this is a nice concpept but it's not as effective as redbull's. I have not seen the downforce numbers, but there are a few things i will point out as to why this is just a gimmick soley designed to show the FIA that they can bend the rules.
I dont think it's very dependable, similar to the front exhuast on the renault.

Mclaren will copy redbull by race 6.

[PlatinumZealot]

@n smikle, awesome job.

Btw, would you be so kind as to show us some pics of the meshes?

Thanks in advance.

The solid-works CFD mesh is a 3d mish-mash of blocks it is not as pretty as Ansys mesh- I can show you but what do you want to see? The fluid cells or the solid cells?

[PlatinumZealot]

@n smikle: Fascinating CFD results there mate, kudos... =D>

I was wondering if you are planning on providing more CFD analysis for Mercedes, Red Bull and Ferrari, in particular. I presume that Ferrari have a similar concept to McLaren, but Red Bull and Mercedes have (so far) used more conservative designs. With regards to Mercedes in particular, it would be nice to see if they are trying to blow the added slot on the diffuser, below the rear light. Any plans?

Thanks again for this...

I am no CFD expert though! but I think I can stick in some exhausts like the Red-Bull's. The RB8 is blowing the beam wing and using the control arms to guide the gas - so It means I have to model the suspension and beam wing accurately before I do a test for that - I will try it when I get the time.

I think the Ferrai might be doing both approaches.. but looking at their outboard exhaust option, they don't have that curved surface coming from the exhaust tip to guide the air downwards - so it may not be as effective as the mclaren's.

[AbulafiaF1]

I am no CFD expert though! but I think I can stick in some exhausts like the Red-Bull's. The RB8 is blowing the beam wing and using the control arms to guide the gas - so It means I have to model the suspension and beam wing accurately before I do a test for that - I will try it when I get the time.

I think the Ferrai might be doing both approaches.. but looking at their outboard exhaust option, they don't have that curved surface coming from the exhaust tip to guide the air downwards - so it may not be as effective as the mclaren's.

Ok, thanks for that... I am also curious as to the Mercedes solution. It does seem to be the more conservative one, in terms of positioning (so far from the rear end). However, do you feel there is a case for F1 teams deliberately not going for too much exhaust blowing this year? I mean, with the off-throttle engine mapping ban this year, too much downforce coming from the exhausts is going to be tricky to handle at corner entries. Even a 2-3% loss in downforce, as soon as the driver is off the throttle, is something that can be felt very intensely inside the cockpit, especially in situations when you are on the limit of adhesion while braking and entering a corner...

To sum up what is a messy post: Do you feel there is a limit in exhaust-produced downforce above which the car becomes unstable to drive? Are the teams, therefore, satisfied with more conventional designs and are not willing (on purpose) to go extra-aggressive on that front?

Finally... Are teams allowed to store exhaust gas in blanked parts of their manifolds and release it as soon as the exhaust pressure on the main manifold goes down? I understand Ferrari were doing just that, last year, and God knows who else.

[CountessBathory]

@n smikle, awesome job.

Btw, would you be so kind as to show us some pics of the meshes?

Thanks in advance.

The solid-works CFD mesh is a 3d mish-mash of blocks it is not as pretty as Ansys mesh- I can show you but what do you want to see? The fluid cells or the solid cells?

Could be any pics of both?

Thank you very much.

[TBone]

This is fascinating stuff - afraid I'm rather new to this so please excuse the lack of understanding but I have the following questions:

1. If the exhaust is deflected more at low speed does this mean that the exhaust flow hits the rear tyres (and hence heats them) more at slow speeds? If so, then presumably this is a real advantage when preparing for qualifying runs, race start and even in getting traction out of low speed corners? If this is the case then might this not present overheating issues during extended safety car periods?

2. Presumably the set up is self regulating - ie, as the deflection of exhaust flow is dependent on air speed rather than engine map/throttle position, would this negate the need for extensive engine mapping to heat tyres as has been suggested above? I may be missing the point slightly if the flow deflection is also dependent on throttle position and clearly the RB7's approach was dependent on the location of the exhaust outlets.

3. Red Bull's current set up is surely not definitive and so they must be expected to display their own interpretation of an exhaust which seals the diffuser, given the amount of rake they are running?

4. I know this thread is mainly focused on the MP4-27 and the exhaust flow impact is also determined by the whole package but what do people think about the effectiveness of the McLaren set up vs, say, the Mercedes or the Sauber?

Many thanks in advance and very interesting reading once again

T

[shelly]

@ringo: the diffuser when it is working has a significant effect on the flow around the footplate, and it suks in air from the sides and from above the footplate.
Vortices generated around the footplate are similar and comparable to those developed around the rear wing endplate.

There was a nice example of them in a thread some time ago, with pitures from ansys.
If you ignore this mechanism you can not understand a big part of exhaust blowing effect.

Ferrari has run a curved convex ramp after exhausts similar to mclaren in jerez test, so the were probably trying something similar