Vodafone McLaren MP4-27 Mercedes

[Pup]

Really??

Sho'nuff, man.

[AdamCarpenter]

I assume our goal to downward exhaust flow. This flow also has a boundary layer and unknown flow quality coming around the side pod. A best you have 3-5 inches after the exhaust pipe opining to force the exhaust downward onto the channel floor. You are trying to push down a high velocity exhaust flow, at its highest levels, with an ambient air flow of questionable quality and strength. It is not going to happen.

Now as you state, the exhaust plume expands and follows the contour of the channel. No need for the Coanda Effect. Now is the Coanda Effect going to augment this flow once it gets to the bottom of the channel, not clear. I would claim that the 'center axis of the exhaust flow' has not been bent in this situation.

Brian

Contradiction here. First, your line of reasoning is that the exhaust plume can't be pushed down to the floor of the channel, then you say that it will expand to follow the contour of the channel. Which is it?

Why do we not mention Coanda Effect when discussing the flow around the side pod?

Maybe because every team's sidepods will make some use of Coanda effect to keep flow attached around curved sections... Whereas McLaren are the only team to have an extended channel protruding past their exhaust exit, which looks like it makes clever use of the Coanda effect in a possible attempt to seal their diffuser. No need to talk about it regarding sidepods because it's common knowledge that Coanda effect (among other things i'm sure) helps teams to keep air flow attached around the sidepods.

[hardingfv32]

And what is the effect of the reduced velocity and pressure drop? The exhaust is at a high velocity and greater pressure level than the ambient surrounding flow, no need for expansion as it clears the exhaust outlet?

Brian

[Pup]

higher velocity = lower pressure

[Owen.C93]

higher velocity = lower pressure

Forced exhaust gas will be high pressure though.

[hardingfv32]

You are trying to push down a high velocity exhaust flow

No contradiction, 'you' is the party I am speaking to.

If you are having a hard time understanding my statements feel free to ask me for a restatement. I will try and make them simpler for you.

Maybe because every team's sidepods will make some use of Coanda effect to keep flow attached around curved sections...

Is this a common talking point in aero literature. Can you state a reference?

Brian

[hardingfv32]

higher velocity = lower pressure

And in the case of exhaust flow, progressively slowing (lower) velocity means higher pressure and expansion?

I just finished a new intake scoop/plenum based on the principal. A couple weeks work, hope you do not prove me wrong.

And you said you did not 'need' to prove me wrong....

Brian

[strad]

Pup...Just showing that all research I find shows the exhaust expanding.
I'm trying to picture the exhaust flow on a typical Comp class dragsters exhaust header...

[AdamCarpenter]

harding, read the two statements of yours that I quoted in my last post. First you say that The exhaust plume isn't going to reach the bottom of the channel, then you say that it will expand to reach the bottom of the channel.

Google defines contradiction as:

1. A combination of statements, ideas, or features of a situation that are opposed to one another.
2. A person, thing, or situation in which inconsistent elements are present.

Both versions of its definition apply to your two statements.

Is this a common talking point in aero literature. Can you state a reference?

No, I can't... That's my point... It ISN'T talked about because it isn't new or exciting with regards to a car's sidepods. Go back and re-read what Coanda effect is, then think about what will happen as air hits the curved outside edge of a sidepod.

[Pup]

Pup...Just showing that all research I find shows the exhaust expanding.

Like I said, it can expand but I don't think it does. What you've shown is what I said about rockets - they shape the bell for a particular ambient pressure and that's why when you look at the plume at liftoff it's nice and narrow but when it's way up in the atmosphere it looks like they've kicked on the afterburners. And that's rockets, not V8's, so...

So, could the exhaust expand? Yeah, like I said, maybe, but I don't think so, depends.

[beelsebob]

higher velocity = lower pressure

And in the case of exhaust flow, progressively slowing (lower) velocity means higher pressure and expansion?

I just finished a new intake scoop/plenum based on the principal. A couple weeks work, hope you do not prove me wrong.

And you said you did not 'need' to prove me wrong....

Brian

Consider why it's slowing – because it's losing energy, this should give you a hint about whether it's expanding or contracting.

[Pup]

Yes and there's also the external pressure bit of the equation; i.e., rising exhaust pressure = progressively reduced rate of contraction.

[simieski]

higher velocity = lower pressure

Forced exhaust gas will be high pressure though.

Maybe time for coanda, flow, pressure and other exhaust related air bending tomfoolery thread split?

With ref to the above quote, I wouldn't imagine the exhaust gas would maintain high pressure for long, I thought pressure only really exists when there is something to oppose flow, once the exhaust gas is out of the pipe and into free air i dont see how it would stay at a high pressure?

[PlatinumZealot]

Yes that anaconda effect is quite handy around curved surfaces.

[hardingfv32]

No, I can't... That's my point... It ISN'T talked about because it isn't new or exciting with regards to a car's sidepods.

I know what it is. It is how it is implemented that we need more 'detailed' knowledge of to know if it applies here. I brought up the side-pod example because it would seem relevant, yet you do not see it brought up in the aero literature. There is a reason we are overlooking.

I am up for learning something new today.

Brian