2012 Exhaust Blowing & Coanda

[myurr]

I too am of the mind that Newey was late to the party with the "McLaren style exhaust". As far as RB being more evolved and mature is a strange comment as in engineering less is more and McLaren's solution is far more simplified and elegant.

The RB solution seems to seriously compromise their own philosophy of ensuring excellent flow around the rear of the side pods over the diffuser.

As I have said before, it makes no sense bringing such a solution to the last test and run the risk of weather and accidents getting in the way of measuring its performance. RB were either behind the curve or massively over confident.

I agree with your last statement, but not the first. What makes you think RB has compromised the airflow around the rear of the sidepods? I don't see it that way, and I don't remember anyone else thinking the same(as you), so I'm just wondering.

Regardless of the other pictures and armchair CFD, there is the simple measure that Red Bull has far more bodywork in the airflow. All of which will compromise the airflow in some regard, either drag, turbulence or blocking another part of the airflow. Take the ramp down from the exhaust, for example. Making the huge assumption that Red Bull and McLaren achieve similar results, the Red Bull design slaps a huge amount of bodywork right where the coke bottle and clear flow to the rear should be. Whilst they have their clever little tunnel under the ramp, if McLaren are able to get the same effect without needing the ramp at all then this is far less of a compromise and will disturb the rest of the airflow far less than Red Bull's design.

[PlatinumZealot]

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 is for a shrouded exhaust.

vc = 1.33 vo A / (A + 10 x2)

= 1.33 q / (A + 10 x2) (3)

This matches my CFD at zero distance. But there is too much going on around the F1 car like desnsity changes, the exhaust curving around the surface and cross winds to really accurately tell how much velocity drops with this equation. This equation might be for an Air conditioning exhaust duct..But let us work with it all the same.

Going by the equation above it says that at 0.4 meters from the outlet the velocity of the exhaust drops to 0.774 m/s (higher than ambient air speed I suppose). This is not matching with my CFD because of the curve the exhaust has to travel around, but I can surely say from looking at the CFD results by the time the exhaust reaches the diffuser it is going barely any faster than the ambient air.

[avatar]

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

I guess that makes it hard to judge the velocity drop off and the effect on attachment of the flow downstream. [edit] unless you have a CFD package as n smikle does:) as seen above.

Depending on the temp drop off, would the boundary layer behaviour be significantly different? Might that change where the flow ends up and its effect on the diffuser aero too?

[Shakeman]

I agree with your last statement, but not the first. What makes you think RB has compromised the airflow around the rear of the sidepods? I don't see it that way, and I don't remember anyone else thinking the same(as you), so I'm just wondering.

The put a load of bodywork, the tunnel, in the way of the flow of air around the side pod to keep the exhaust separate.

McLaren's solution seems to do that without using a tunnel looking at nsmickle's cfd plot.

I'm no aerodynamicist just a former nuclear engineer turned animator so my opinion counts for 0!

[mozza_84]

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[/quote]

Probably[/quote]

Not buying it. Newey's solution is much more evolved and mature. He just waited to show it.[/quote]

you do know that the dosnt shine out of adrian neweys you know what he has copied and twisted mclarens and saubers idea simple as.

[Crucial_Xtreme]

Regardless of the other pictures and armchair CFD, there is the simple measure that Red Bull has far more bodywork in the airflow. All of which will compromise the airflow in some regard, either drag, turbulence or blocking another part of the airflow. Take the ramp down from the exhaust, for example. Making the huge assumption that Red Bull and McLaren achieve similar results, the Red Bull design slaps a huge amount of bodywork right where the coke bottle and clear flow to the rear should be. Whilst they have their clever little tunnel under the ramp, if McLaren are able to get the same effect without needing the ramp at all then this is far less of a compromise and will disturb the rest of the airflow far less than Red Bull's design.

Yeah I see what you're saying and ultimately agree yes it is a compromise of sorts. But I was thinking about the overall intended consequence of their system. Perhaps they do sacrifice a bit in comparison to McLaren, but perhaps there are performance benefits to their solution that override the need to have completely unobstructed flow to the rear coke bottle area.
Do you see what I'm saying?

@Shakeman no worries mate, I totally get where you're coming from. I have a computer science degree so I'm further off than you.

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[hardingfv32]

I believe Newey does everything for a reason even if it's unbeknownst to us. He could have chosen many different solutions, but chose this one. Obviously he knows something we don't and I wouldn't pretend to be of equal knowledge with him.

ALL the teams do everything for reason and we have no idea why. This is some thing new to this forum?

We also know the the teams are not going to tell us what is going on, so if you are interested in knowing like me, then we have to solve the puzzle on our own.

Brian

[Th0R]

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.

1) Expand on 'the extension of the air due to a high temperature gradient'.

2) Of coarse there is no way for us to know if the air stream helps or hurts exhaust gas concentration.

Brian

1) what happens exactly isn't that easy to say. A basic introduction to expansion: http://en.wikipedia.org/wiki/Thermal_expansion I am afraid that i dont have a good cfd software avaiable at the moment. So i am not able to generate some images. The ones posted in some threads here didn't seem very accurate.

2) i think it is not arguable that the bodywork is designed to help the air flow not to disturb it

[hardingfv32]

I guess that makes it hard to judge the velocity drop off and the effect on attachment of the flow downstream. [edit] unless you have a CFD package as n smikle does:) as seen above.

Depending on the temp drop off, would the boundary layer behavior be significantly different? Might that change where the flow ends up and its effect on the diffuser aero too?

But we can make better judgments if we have some idea what the range of exhaust flow velocity is.

The exhaust temp drop off is very high. From 850 C at the exhaust port to about 100-200 C at the exhaust tip. I do not think the exhaust flow is always outward bound. There could be some reversion flow that introduces cooling near the exhaust tip. I know I have to be concerned about reversion when I am developing a cylinder head.

Brian

[Crucial_Xtreme]

I believe Newey does everything for a reason even if it's unbeknownst to us. He could have chosen many different solutions, but chose this one. Obviously he knows something we don't and I wouldn't pretend to be of equal knowledge with him.

ALL the teams do everything for reason and we have no idea why. This is some thing new to this forum?

We also know the the teams are not going to tell us what is going on, so if you are interested in knowing like me, then we have to solve the puzzle on our own.

Brian

Yeah I agree Brian. I said in a post after yours, that I agreed it was a compromise of sorts, but only for what could be intended as a greater benefit. Or at least their desire to achieve as much.
Obviously they want to keep the flows separated as much as possible but it seems to me that Newey placed more emphasis on trying to get the exhaust to do what he wanted versus ensuring unobstructed air flow to the rear coke bottle area. So while I think it can be classified as a compromise, in fact it's exactly what he wanted to do so is he really compromising anything?

[hardingfv32]

They also might feel their solution is less subject rule litigation.

Brian

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[myurr]

Regardless of the other pictures and armchair CFD, there is the simple measure that Red Bull has far more bodywork in the airflow. All of which will compromise the airflow in some regard, either drag, turbulence or blocking another part of the airflow. Take the ramp down from the exhaust, for example. Making the huge assumption that Red Bull and McLaren achieve similar results, the Red Bull design slaps a huge amount of bodywork right where the coke bottle and clear flow to the rear should be. Whilst they have their clever little tunnel under the ramp, if McLaren are able to get the same effect without needing the ramp at all then this is far less of a compromise and will disturb the rest of the airflow far less than Red Bull's design.

Yeah I see what you're saying and ultimately agree yes it is a compromise of sorts. But I was thinking about the overall intended consequence of their system. Perhaps they do sacrifice a bit in comparison to McLaren, but perhaps there are performance benefits to their solution that override the need to have completely unobstructed flow to the rear coke bottle area.
Do you see what I'm saying?

@Shakeman no worries mate, I totally get where you're coming from. I have a computer science degree so I'm further off than you.

Don't get me wrong, *if* they have better exhaust flow / positioning than McLaren then it's possible that the benefits far outweigh the disadvantages. However if McLaren are getting similar benefits from the exhaust then their solution is the more elegant with less compromise elsewhere on the car.

[RaceFaceXC]

Honda has been approaching 110% VE on its USDM and JDM Civic Si road vehicles. But it is important to know that this 100%+ VE number is only possible due to pressure wave tuning and to a lesser extent some other clever port and cam designs, AND that it only achieves the 100%+ VE performance at very narrow RPM bands. Without a variable runner/primary length intake/exhaust I dont know if it would be possible to broaden this range of 100%+ VE. Rumor is that the new Mazda SkyActive program will be developing engine designs more efficient than the Honda design for VE but no numbers have been published on flow that I know of.

Back on the exhaust topic, is that a VG in the exhaust exit on the graphic posted by hardingfv32? If so, I thought VG's were not allowed in current F1 regs. If not, what is that small swept leading edge "bump" in the high energy part of the exhaust stream?