Exhaust Blown Floor - Forward Exhaust Exit

[hardingfv32]

1) "At +200kph hardly any deflection of water spray along the floor visible, so my thinking is almost all exhaust goes under the floor and leaves somewhere between rear wheels"

What would be the benefit of this condition?

2) What section/area of the diffuser benefits from increased airflow?

Brian

[ringo]

Saying the car is stationary ... It's just irrational.

The exhaust plume shape will not be the same at 300kph and 0kph. It's irrational to expect otherwise.

Why are you being so tough headed?

You just siad the car didn't move!! it moved in the video!!!

I already said this.

The exhaust plume shape will not be the same at 300kph and 0kph

It's nothing new!!!
The exhuast does not go under the car for christ sake!!! Jeez

I also made a simulation of the car going all the way to 205 mph. It did not flow to the center of the diffuser!!

I swear these guys just want to prove me wrong in at least 1 thread.
Even when they know they are repeating the same exact thing i demonstrated painstakingly.

I give up. This is just some sick joke to play ignorant. Can somebody with sense summarize the whole thread please, and let these guys know they are talking clap trap as segudenum would say?

It's all there:

viewtopic.php?f=6&t=9450&start=435

These clowns just rehashed exactly what i was saying earlier. The same things they never believed because Some bogus insider info.

The bogus inside scoop failed them, so now they are languishing for something to cling to. Ironically they cling to the same theory they rejected for the past 3 months.
Now Marek has just seen the light and is talking as if no one ever brought up the theory. Oh Lordy!!!

[ringo]

1) "At +200kph hardly any deflection of water spray along the floor visible, so my thinking is almost all exhaust goes under the floor and leaves somewhere between rear wheels"

What would be the benefit of this condition?

2) What section/area of the diffuser benefits from increased airflow?

Brian

I said this before, Human thinking cannot predict these things. Read the link i posted in my previous post. Don't just look on the picture marek posted, i have countless shots with the car going high speeds and still blowing wide.

That shot marek has is also misrepresented, as water spray is not the exhuast pattern. Its only a loose guide. You can't actually see the exhuast, and the water wont be pushed everytime as that is dependent on the dept of the water and the speed of the car over the water.

This thing is designed to work in the corners. A car doesn't take a corner at 200mph. So the diffuser flow logic is ill conceived.

[Formula None]

it moved in the video!!!

About how fast would you say it was going? 50kph? The plume will change shape at higher air speeds.

water spray is not the exhuast pattern. Its only a loose guide. You can't actually see the exhuast,

So why are you then pointing to other photos & videos as evidence?

[shelly]

[quote="ringo] The exhuast does not go under the car for christ sake!!! Jeez

[/quote]

You have no proof of this, try to substantiate it with some line of reasoning.
Also it seems that you do not read or understand others' post.
As Formula None noted, you alsokep contradicting yourself, so read agin your posts also.

[malcolm]

There is some obvious visual evidence that the FEE isn't designed to feed the rear diffuser:

1) The exhaust isn't pointing backwards... if they wanted to feed the rear diffuser it would point directly backwards.

This is a great point that I think was missed (I had that idea too, but found that Speeed24 mentioned it earlier in the thread).



However, if you look at it another way, it still may end up going under the car.

Case one:

^^this image shows potential exhaust flow, relative to a completely free stream parallel to the centre-line of the car (no pressure effects from sidepods, splitters, tires, diffuser, etc).

Now, if we take into account the low pressure zone generated at the diffuser mouth, you would certainly expect the flow to bend inward, correct? Just using imaginary fluid dynamics simulations (IFD!), I would expect the median line to end up roughly near the inside edge of the rear tire and then obviously pushed in further by the effects of the tire itself.

What do you think, Ringo? Your plot shows that a large part of the stream would hit the rear tire in a free stream, but with the effects of the diffuser, wouldn't more of that flow be pulled in toward the diffuser?



Case 2:

^^Lola Champ Car.

Of course, the aero won't be identical, but it gives an idea of how air would tend to flow back it toward the diffuser (or in this case, the tunnels). Seeing that Mike did the wind-tunnel work for Panoz on the last Champ Car, I'd say his depiction of airflow is pretty close.

Given that, if you look at the fourth red line from the centre, it still comes back in to what would be a diffuser on an F1 car.

Now, given that the exhaust flow is mixing with the ambient flow, wouldn't you expect at least half of the exhaust flow to end up making its way to the diffuser?





Last thing: Ringo, can you dig up those CFD sims and show a vector plot? I'd like to see where the flow is aiming... Right now it still looks like some of flow from the exhaust could end up under the diffuser...

[marekk]

It's long thread now, and we've already discussed diffuser influence (even posted Toyota CFD of the real car with clearly visible flow lines under the car).
I think we all agreed this is significant.

We've discussed why it could be better to not blow directly to the rear a few weeks ago.

I really appreciate ringo's cfd (i know how much work you have to put into this), but to get usable results one have to use terabyte-range datasets (with detailed real car model) and use one of moving meshes techniques to simulate at least the tarmac and rotating tyres (not to mention aeroelasticity effects). On "normal" PC (even strong one) solver run will take ages to finish. Even on 10TFlop, 1TB RAM cluster much simpler models run for hours/days.

We will probably never know for sure how it really works, but lot of fun speculating about it (at least for me) anyway, and always something new to learn.

[malcolm]

Ok, with that in general agreement then, then why does Ringo think that the exhaust is somehow immune to this effect?

(no sarcasm there, genuinely curious... and sorry if I missed it in a prior post)

[hardingfv32]

Does increased flow (air and exhaust) over and under the side pod and diffuser create more net down-force? Does the flow increase have to be equal, top and bottom for best effect?



Brian

[ringo]

There is some obvious visual evidence that the FEE isn't designed to feed the rear diffuser:

1) The exhaust isn't pointing backwards... if they wanted to feed the rear diffuser it would point directly backwards.

This is a great point that I think was missed (I had that idea too, but found that Speeed24 mentioned it earlier in the thread).

Yeah right.

However, if you look at it another way, it still may end up going under the car.

Case one:

^^this image shows potential exhaust flow, relative to a completely free stream parallel to the centre-line of the car (no pressure effects from sidepods, splitters, tires, diffuser, etc).

I created that image. So you can't tell me anything about it.
The blue line is not a practical value, neither is the green. Those are worst possible cases, on the extremes of certain fluid Behavior. It was outlined in the scholarly article.

Secondly the blue line doesn't go under the floor because the tyre is there.
It crashes into they tyre.

This simulation was ignoring the rear wheel.

[ringo]

I really appreciate ringo's cfd (i know how much work you have to put into this), but to get usable results one have to use terabyte-range datasets (with detailed real car model) and use one of moving meshes techniques to simulate at least the tarmac and rotating tyres (not to mention aeroelasticity effects).

I considered moving wheels and ground. Even the ground roughness is considered and tyre surface roughness.
You don't need terabyte range whatever you are saying. That's just techno babble, which you have no experience with.

On "normal" PC (even strong one) solver run will take ages to finish. Even on 10TFlop, 1TB RAM cluster much simpler models run for hours/days.

I know how to use the PC resources well. Day long calculations are overkill. The differences are very minute, and the effort is not worth it if it will only be rejected because some guy says his cousin knows someone working in F1.

[hardingfv32]

Ringo

Please explain the air flow issues, with no exhaust flow, in regard to the side pod and diffuser. How is the their design normally optimized?

Brian

[malcolm]

However, if you look at it another way, it still may end up going under the car.

Case one:

^^this image shows potential exhaust flow, relative to a completely free stream parallel to the centre-line of the car (no pressure effects from sidepods, splitters, tires, diffuser, etc).

I created that image. So you can't tell me anything about it.

The blue line is not a practical value, neither is the green. Those are worst possible cases, on the extremes of certain fluid behavior. It was outlined in the scholarly article.

Secondly the blue line doesn't go under the floor because the tyre is there.
It crashes into the tyre.

This simulation was ignoring the rear wheel.

I know you created the image, and yes I can tell you something about it.

(quick note: I was restating what you had done to explain my case, not telling you how you did what you did)

Since you didn't bother to read (or comprehend, or reply to) what I wrote, I will restate it.

This image shows a free stream, where the car does not interact with the flow

You know that, since you created it. Right?

NOW, once we take into account that the diffuser generates low pressure, obviously that exhaust stream would be drawn back in, correct?

Since that blue line would theoretically crash into the rear tire in a free stream where the rear tire (and the rest of the car) had no effect on the air (which is what you just said), then if you take into account the effects of the diffuser and the tire, then that blue like would likely end up going inside the rear wheel and SURPRISE, SURPRISE, through the diffuser.

Therefore, if some of the exhaust stream ends up following that blue line, then SOME of it may end up going through the diffuser.




I do agree with you that the effect is probably largely to fill in the front tire wake (your CFD shows that quite well) and to heat the air at the leading edge of the floor, but your hard-headed stance that no exhaust will possible go into the diffuser is quite frankly unfounded (unless there are some vector or streamline plots that you are withholding... which is why I asked if you had them so I could better understand roughly where the air would go).






Oh, and don't be a jerk.

[ringo]

Sorry i thought you were Marekk.

I was rushing to leave work, and dropped in a quick post. I didn't look long enough on the page.

[malcolm]

Haha, ok.

Awaiting your less-hurried reply, then!