2012 Exhaust Blowing & Coanda

[GrizzleBoy]

I also cant help but feel that McLaren is waiting to add some kind of upgrade to where that tape is on the floor.....it just doesn't fit in with their desire to have their car be pretty and perfect(at least aesthetically) for it to be something that's going to be there for the rest of the season.....

1) Have you ever seen any discoloration of this tape?

2) What better way to misdirect the competition with a falsely placed piece of tape. The body prep department probably smiles every time they put the tape in place.

Brian

You are hinting at something to do with exhaust fumes for you to ask me about discoloration, but I never specified what I thought the upgrade could be because I don't really know, let alone if there will be one.

I just have a feeling that something much more efficient than tape is going to end up there later on in the season.

[hardingfv32]

I think the major difference between Brian's example and mine is the velocity of the airflow. I do think that the slower flame more closely matches the exhaust flow.

What is the difference in the flow between the two types of flame? Which do you consider faster? I am not sure how to judge my acetylene flame. I could use the length as a guide and double the size of the flame. The softest (shortest and lowest gas pressure) seemed to provide the best Coanda Effect, so that is what I used.

Brian

[Pup]

There´s no magic force that will pull the exhaust gases down to the floor.

I trust that Mr. Lowe isn't relying on magic.

Though I'm considering going down to the local witch doctor this weekend to see what he's got for pit stops.

[Nando]

To be honest i find the Cyan line to be more close to reality considering the immense velocity of the exhaust gases.

The fact that they would simply bend downwards due to Coanda effect i can´t really see.
But then again, i never studied aero.

The ferrari for example is a perfect example. Sidepods shaped to use as much of the downwash as possible to push the gases down to either the diffuser or brake fins.

[hardingfv32]

If you don´t aim it at something then you won´t have much of an effect at all.

The angle restriction of body work in relation to the exhaust outlet is actually 3 deg. 10 deg relates to the angle of the exhaust pipe axis.

So the issue of Coanda Effect on the surface of the bodywork (channel) at the exhaust outlet is a little less than ideal. It is not easy to measure 3 deg in my experiment, so I did not try to demonstrate that aspect of the current system.

Brian

[Nando]

The angle restriction of body work in relation to the exhaust outlet is actually 3 deg. 10 deg relates to the angle of the exhaust pipe axis.

So the issue of Coanda Effect on the surface of the bodywork (channel) at the exhaust outlet is a little less than ideal. It is not easy to measure 3 deg in my experiment, so I did not try to demonstrate that aspect of the current system.

Brian

See if i understood you right here.

The exhaust tip can be no less then 10 degrees.
The exhaust housing can not follow the exhausts but has to "expand" by 3 degrees.

?

[hardingfv32]

Yes... This has been discussed a long time ago.

Brian

[GrizzleBoy]

The angle restriction of body work in relation to the exhaust outlet is actually 3 deg. 10 deg relates to the angle of the exhaust pipe axis.

So the issue of Coanda Effect on the surface of the bodywork (channel) at the exhaust outlet is a little less than ideal. It is not easy to measure 3 deg in my experiment, so I did not try to demonstrate that aspect of the current system.

Brian

See if i understood you right here.

The exhaust tip can be no less then 10 degrees.
The exhaust housing can not follow the exhausts but has to "expand" by 3 degrees.

?

I'm sure I remember something about the limitations of an outward cone extending in front of the exhaust being set at no less than three degrees outward during the Jerez/Barca testing season.

[Nando]

Ok thanks Grizzle!

Yes... This has been discussed a long time ago.

Brian

Then that makes the Coanda effect even more unlikely imo.

If we assume the exhaust gases gets horizontal just as they exit the exhaust, how is it going to be pulled down?

We can see the Mclaren layout having the exhaust housing aimed downwards slightly but more importantly outwards.

If the coanda effect really sucks the exhaust gases down to the floor then it should also work in a horizontal way by pulling exhaust gases inwards.

So know you have the coanda effect in two directions which would dissipate the exhaust gases?
It would react as a flower opening up for the first time.
except not in 360 degrees.

Seems a bit far-fetched imo.

[hardingfv32]

To be honest i find the Cyan line to be more close to reality considering the immense velocity of the exhaust gases.

The exhaust velocity is NOT 'immense'. The exhaust leaves the exhaust seat/valve area at about 280 m/s and slows to something near 100 m/s at the exhaust tip. Again, this was discussed in the '2012 Exhaust Blowing Thread' in early March.

Brian

[raymondu999]

I just can´t see how the shape of the housing can in any way re-direct the exhaust gases downwards. imo it has to be pushed down and be contained by air to reach it´s destination.

The pressure is at the surface - not at the floor. There is a low pressure area between the plume and the convex (unless I'm mistaken the object/surface has to be slightly convex - maybe Pup or Brian can verify?) sidepod shape which then sucks the plume, keeping it sort of "attached" to the sidepod.

It's not "pushed" down, but in effect, "pulled" down by the low pressure zone. The Coanda in itself is nothing to do with the downwash airflow nor the housing "redirecting" it down.

Here: http://bit.ly/igoPch (it's the coanda effect wiki page - but there's the funky "ä" in the webpage which is screwing up the normal link)

[hardingfv32]

If the coanda effect really sucks the exhaust gases down to the floor then it should also work in a horizontal way by pulling exhaust gases inwards.

The McLaren channel is just for a downward flow. The flat or straight vertical surfaces of the channel would not provide any Coanda Effect.

Brian

[Nando]

To be honest i find the Cyan line to be more close to reality considering the immense velocity of the exhaust gases.

The exhaust velocity is NOT 'immense'. The exhaust leaves the exhaust seat/valve area at about 280 m/s and slows to something near 100 m/s at the exhaust tip. Again, this was discussed in the '2012 Exhaust Blowing Thread' in early March.

Brian

100m/s is exhaust gases exiting the car at 360km/h.
If that isn´t "immense" then i don´t know what is.

I simply cannot believe that a coanda effect that does not interact with anything at all can pull down exhaust gases that come out at 360km/h.

[raymondu999]

I simply cannot believe that a coanda effect that does not interact with anything at all can pull down exhaust gases that come out at 360km/h.

It's interacting with the low pressure zone at the surface! It's not being sucked to the floor - it's being sucked to the sidepod face, which in turn terminates near the floor...

Coanda is not downwash. Two different things in this context. Coanda is a suction thing caused by a low pressure zone as you put the fluid next to a convex object/surface

[Nando]

If the coanda effect really sucks the exhaust gases down to the floor then it should also work in a horizontal way by pulling exhaust gases inwards.

The McLaren channel is just for a downward flow. The flat or straight vertical surfaces of the channel would not provide any Coanda Effect.

Brian

Yea it has a downwards flow. Which further increases the distance from where the exhaust gases leaves the tip to where the bodywork starts.

If we assume the exhaust gases are getting pulled down so they are horizontal then you would still have some gap between the exhaust gases and the bodywork.

you would have to put something in front of the gases (not directly in front but for sure in the way even if it´s 10% of the exhaust gases) for the gas to interact and get pulled downwards.

There is no such thing on any of the cars frankly, all exhaust gases are released right into free air thanks to the 10 degree rule.