2012 Exhaust Blowing & Coanda

[Adrian Newby]

To moderators,
I have been reading these forums everyday for 2 yrs now..

this is getting out of hand here...

...you're more than welcome to join.

Yes, please. Especially if you can add any large nuances that we've missed. We have moved on to ever-smaller ones because none of us are bright enough to come up with any new big ones!

But, as Bhall said previously, I think it has been a very good discussion overall. And I do have to credit the quality of the opposing posters, even if we disagree.

[hardingfv32]

[quote="beelsebob"
1) The figure calculated was based off an exhaust gas exit speed 2.5 times too fast
2) The figure calculated was based off air flowing around the exhaust exit at 0m/s, not at 75-100m/s.
3) The figure calculated was 30m/s, even under the above broken conditions.
4) The model that figure came from was a model of the McLaren, not the RBR.
5) The model showed the air hitting the floor almost straight downward, and losing all its speed there, which would likely not happen if it was being dragged backward by ambiant airflows.
6) The only way you got to 5m/s was by guessing.[/quote]

1) I have done a lot of research on SI engine exhaust 'tip' velocity and have found almost nothing. Do you have a source of information? I know the Mean Gas Velocity at the exhaust valve is in the range of 284 m/s. I also know the exhaust system has at least 225 deg of bends in it and that the is a 25% loss in velocity every 25 deg of bend.

The exhaust tip velocity is a calculation. I should be able to provide it if you want to crunch the numbers.

4) I am using the sim to develop an understanding of the exhaust velocity after it leaves the tip. Research on this point has turned up absolutely nothing. This sim is the this bit of understanding we have of how fast the exhaust slows or is absorbed after leaving the tip. Do you have any info on this subject?

5) I am have made no attempt to discuss the validity of the sim. you could go to the aero section and post your question.

6) I have stated the reasoning for my number. Crunch some numbers and develop a different number if you wish.

The fact that at least 2 teams are trying to direct their exhaust flow there, one of whom appears to have the fastest/second fastest car suggests that it makes a worth while difference, even at the reduced potency.

These two cars held this same performance status at the end of last season 'without' the current exhaust system. You can not demonstrate any correlation. It would be my claim that the current exhaust is so neutered, that if their exhaust systems are wrong they would still hold the same performance status.

Brian

[Crucial_Xtreme]

Can some of you explain how long the running time is designing and manufacturing on an update red bull introduced last week? Some people in the f2012 thread seem angry why Ferrari cant produce such in 3 weeks time.

A brand new front wing can be made from mold to autoclave to paint to decals in 48 hours. Sidepods, roughly a week depending on their complexity. When Horner or Newey spoke of their new design, it was from drawing up, running sims then making the pieces. IMHO.

[kilcoo316]

A brand new front wing can be made from mold to autoclave to paint to decals in 48 hours. Sidepods, roughly a week depending on their complexity. When Horner or Newey spoke of their new design, it was from drawing up, running sims then making the pieces. IMHO.

Exhausts take much longer than this though.

[Adrian Newby]

I saw an interview with Christian Horner saying something to the effect of "The updates you are seeing today were begun a month ago". And he was talking about the new exhaust.

I have to say, I'm somewhat surprised! I'd have thought they would have spent longer gearing the design around the exhausts. Its a pretty fundamental change in position to only have started a month ago.

Unless it was a month in manufacturing?

I really don't know how specific he was being about the time frame. It seems he was mainly trying to dispel the notion that Red Bull had copied anything from any of the other cars after the start of testing, so it may have been "at least a month".

A month is still a very healthy chunk of an F1 teams' offseason, though, so they have to move pretty fast. And I would imagine Adrian Newey had been cogitating about it for quite a long time before that. So, who knows...

[hardingfv32]

To what extent have people factored temperature/ differing fluidity into their models?

The tip velocity calculation accounts for temp. Again, there is little information available on exhaust tip temps.

Brian

[Crucial_Xtreme]

A brand new front wing can be made from mold to autoclave to paint to decals in 48 hours. Sidepods, roughly a week depending on their complexity. When Horner or Newey spoke of their new design, it was from drawing up, running sims then making the pieces. IMHO.

Exhausts take much longer than this though.

Yeah I agree, depending on how large the difference is on the changes. Reading the F2012 thread I believe he was mainly talking about bodywork accommodating their revised exhaust position.

As for the RB8, I think Newey had an idea of what he wanted to do, but probably didn't pull the trigger on it until they got to Jerez and saw the different solutions from different teams. I remember him saying he thought the Sauber solution was interesting. So I guess that could very well mean they were already working on them though.

[hardingfv32]

You do not want to make a vortex with the exhaust: you just want to alter the advance ratio of the corkscrew of the existing footplate vortex,

What do you envision as being required by the exhaust flow to 'advance ratio of the corkscrew'? Does the exhaust flow need to be aligned with the vortex axis?

I understand how the footplate would generate a vortex done stream, but wouldn't the formation process require some leakage by definition. I would think the vortex needs to be formed ahead of the footplate to get a net pressure reduction. Could this be what the strake is for?

Brian

[hardingfv32]

its just about 5 guys talking on this forum and sticking to small nuances which we are eye balling from pictures.

You know the five guys... so don't read their posts. Is that soo hard?

You are always free to post anything new you wish. Feel free to develop a new theme.

Brian

[Adrian Newby]

A brand new front wing can be made from mold to autoclave to paint to decals in 48 hours. Sidepods, roughly a week depending on their complexity. When Horner or Newey spoke of their new design, it was from drawing up, running sims then making the pieces. IMHO.

Exhausts take much longer than this though.

Yeah I agree, depending on how large the difference is on the changes. Reading the F2012 thread I believe he was mainly talking about bodywork accommodating their revised exhaust position.

Yes, to clarify what I said previously, Christian was talking about the new update package in general, not the exhaust in particular, but it was the update that included the new exhaust.

[marekk]

4) I am using the sim to develop an understanding of the exhaust velocity after it leaves the tip. Research on this point has turned up absolutely nothing. This sim is the this bit of understanding we have of how fast the exhaust slows or is absorbed after leaving the tip. Do you have any info on this subject?

Brian

Hope this one helps:



Equations:

vc = q / (4 π x2) = vo*π*d2/(48 x2)

where q = volume flow, d - exhaust pipe diamter.

Hardly a jet after 0,5m

source:http://www.engineeringtoolbox.com/exhau ... _1008.html

[hardingfv32]

And he was talking about the new exhaust.

Well the exhaust is not going to take that long. Once the computer has developed the exhaust layout a tooling request can be sent to the CNC machines to make any additional new tooling needed for the fab process. The pieces for the system can also be machined at this time. I would allocate no more than 8 hrs to assemble the fixturing and maybe 8 hrs to weld the system up. I personal could weld it up in about 24 hrs, although my TIG welds will not be as perfect has the F1 guys.

Remember , this can be done in house or with a subcontractor. The subcontractor is paid to maintain machining capacity and personnel availability this time of year for just such rush jobs.

So the exhaust system is not dragging down the update schedule.

Brian

[hardingfv32]

I would imagine Adrian Newey had been cogitating about it for quite a long time before that.

Adrian Newey COPIED the competition. Happy to burst your bubble! What a brilliant idea!

They needed less than one week to make their copy after seeing what the other guys were up to.

Brian

[FakeAlonso]

I would imagine Adrian Newey had been cogitating about it for quite a long time before that.

Adrian Newey COPIED the competition. Happy to burst your bubble! What a brilliant idea!

They needed less than one week to make their copy after seeing what the other guys were up to.

Brian

Probably

[Th0R]

4) I am using the sim to develop an understanding of the exhaust velocity after it leaves the tip. Research on this point has turned up absolutely nothing. This sim is the this bit of understanding we have of how fast the exhaust slows or is absorbed after leaving the tip. Do you have any info on this subject?

Brian

Hope this one helps:

...

Equations:

vc = q / (4 π x2) = vo*π*d2/(48 x2)

where q = volume flow, d - exhaust pipe diamter.

Hardly a jet after 0,5m

source:http://www.engineeringtoolbox.com/exhau ... _1008.html

This model lacks two very important influences you cant ignore.
First of all the extension of the air due to a high temperature gradient, which will itself induce a significant speed. And second the air stream flowing around the exhaust, which keeps the exhaust gas concentrated in a clear stream.