Exhaust Blown Floor - Forward Exhaust Exit

[marekk]

New iteration of FFE for Melbourne ?.
Exhaust's inner wall angled more to the rear, changed shape of heat shield. Definitely all of pipe's exit under leading edge of this shield, but i don't see it blowing downwards - looks rather strictly horizontal to me.

[shelly]

Exhaust blows horizontally, and then pressure gradients make the jet deflect.

[marekk]

Is there any chance that with virtual skirts (the rest of the flow!) not so much air will rush in from the sides and they might be trying to create a vacuum under all the floor, even if at the cost of choking the diffuser a bit?

I don't belive there is any significant air curtain (skirt) effect - for it to work, flow must be much quicker then surrunding air (which is at car's speed) and with well defined boudary.

A bit of vacuum, pulling all over the floor could mean a lot of downforce. The total atmospheric pressure is 10000Kg/m2, that's a lot of potential by just a few % pressure change. The car would suffer in the fast bits, though.

There is veritcal component of gas contraction which uses this big area to produce some downforce.
At high speeds gases go quickly, without much cooling, almost straight to the rear, so it works then just like plain blowed difuser. It could be even more efficient in this operation mode then competitor's solutions. But agree, biggest gain should be visible in slower corners.

[marekk]

Exhaust blows horizontally, and then pressure gradients make the jet deflect.

Yeah. We agreed on this already. I reffered to Scarb's explanation.

[Raptor22]

shes' jsut trying to windme up by persisting with calling it a jet.


Please measure the impulse of the exhaust.

[shelly]

Exhaust blows horizontally, and then pressure gradients make the jet deflect.

Yeah. We agreed on this already. I reffered to Scarb's explanation.

Sorry I misinterpreted your post

[marekk]

shes' jsut trying to windme up by persisting with calling it a jet.


Please measure the impulse of the exhaust.

I think we can describe this flow near the axis for a length of about 5 pipe's diameters as jet. Much quicker then surrounding air, quite well defined boundary. What other word would you use ?

[Raptor22]

Ihave no issue with the initial zone approximately 5D outside the exit. its the rest of it thats not a Jet.

The zone 5D outside of exit is also very dependant on rpm.

its not supersonic flow and its not bounded by supersonic flow either. Its "jet" like behaviour is very limited for reach so to describe it as a bending jet is not correct. Once past the leading ecge of the floor its just hot turbulent gas mixing with cold turbulent air.
Its exhaustin into an area where air flow close to the ground is in the direction of travel of the car and the mixing with air coming off the splitter. It's vector is a resultant somewhere between those flows.

It is not a hose pipe like flow being deflected. Its not operating within a defined boundary e.g. significantly denser flow or Supersonic flow

[ringo]

ala Scarbs

"Front Exit Exhaust


Renault Front Exit Exhaust: Flow passes wide around the floor before entering the diffuser

Renault meanwhile turned the problem on its head. As the aim of the EBD is to increase flow under the car, they pointed their exhaust at the front of the floor. I’ve had it confirmed to me by two ex-Renault sources that the exhaust does indeed mainly flow under the floor.



The exhaust pipe outlet sits above the step plane just ahead of the leading edge of the floor. This is not simply blowing out horizontally and across the floor, but is ducted slightly to blow downwards and backwards, this is roughly in line the with the flow trailing off the “V” shape above the splitter. Along with the strong vortices set up by the splitter, vanes and bargeboards, this makes the floor appear wider than it is. The flow will go out beyond the floor and then curl back in and under the floor. Some flow will inevitably pass over the floor, but the most of the energy will be driving more flow under the floor to the diffuser."

So can we lay this to rest now. and No Ringo, its not what you were sayig all along.

no quote no care, he still changed his tune. I said some stayed up and some stayed bellow. I mentioned it going to the edges of the floor.
So why scarbs said this:

this makes the floor appear wider than it is. The flow will go out beyond the floor and then curl back in and under the floor. Some flow will inevitably pass over the floor, but the most of the energy will be driving more flow under the floor to the diffuser

this is all observed from my CFD. So nothing new here. This is just different words to explain the fluid skirt as manchild put it.
Just admit there was an about turn.

Secondly why ask ex renault sources, why not quote them as well? They are correct of course, but a quote would be nice.






there are no conflicts here with the new tune.

Is there any difference here with what i had here a month ago?
Be honest and don't focus on proving me wrong at all costs.




There was a change of tune, and i am very content.
Though i would rather some quotes from a current renault employee.

Look on it unbegrudgingly and tell me what's wrong with the CFD, see where the gasses go both top and bottom. But most of all notice there is no 90 degree turning coming out the pipe.
I rest my case.

I think certain posters do Scarbs a disservice. He always writes that he suspects or it's probable. He never declares anything. He also updates as more things come to light. But some posters believer that he declares things as absolute facts, which is not so.
So they end up with egg in their face, as their source has simply readjusted and they are left hanging in mid air.

[ringo]

Exhaust blows horizontally, and then pressure gradients make the jet deflect.

The pressure gradient is actually the static pressure before the rear wheel. That's the plain fact.



see the green and red?

It's all there, posted ages ago.

That rear wheel causes the gas to deflect to the inside.

However renault only have diffuser blowing over a particular speed.
The flow of exhuast will vary with engine speed and road speed.
I guess at monaco they will run a pipe with a tighter angle.

[ringo]

New iteration of FFE for Melbourne ?.
Exhaust's inner wall angled more to the rear, changed shape of heat shield. Definitely all of pipe's exit under leading edge of this shield, but i don't see it blowing downwards - looks rather strictly horizontal to me.

it will change as they see fit.

[marekk]

Is there any difference here with what i had here a month ago?
Be honest and don't focus on proving me wrong at all costs.

Anyone to remeber those posts ?

Increase diffuser efficiency how?
Why does the exhuast have to go to the diffuser, why not into the tyres or wide of the car.

So it follows that the exhuast cannot force itself to go along the center line and come out the diffuser. The angle of the pipe is simply too wide.

This pic is with the pipe bellow the step plane, which is illegal, and i think i posted this already.
I went to all lengths to get the thing to blow under the diffuser, i even turned the pipe more downstream than Renaults interpretation and still the air wont stay underneath completely.
And this is with a very low velocity exhaust, to make things easier.

I'll shut up now until sunday's race.

[ringo]

that is not incorrect.

look what you just quoted and think again, you are making yourself look silly:

So it follows that the exhuast cannot force itself to go along the center line and come out the diffuser. The angle of the pipe is simply too wide.

This pic is with the pipe bellow the step plane, which is illegal, and i think i posted this already.
I went to all lengths to get the thing to blow under the diffuser, i even turned the pipe more downstream than Renaults interpretation and still the air wont stay underneath completely.
And this is with a very low velocity exhaust, to make things easier.
the exhaust only goes to the diffuser by the tyres, nothing else.

^^ this is 100% correct. so i don't see the point in quoting me on it. Crticisize my images if you can. But you can't.

I could quote you or anyone else on miles of rubbish posted in this thread about the exhuast but i wont, because the cfd is self explanatory and it's correct.
So i don't have to troll or bait. I don't have to get into a war of words either, because no one in here dare to look at the cfd and point out what is incorrect.

The CFD was always correct, and your main source has went from his original idea to something similar to mine.

So as i say i am quite happy. I did stick to my story, and anyone being objective would agree. No silly twists and turns required.
I never changed anything.

I never, never , never, nevver,.... I never change !!!

[horse]

It's a bit hard to tell with these two what is exhaust and what is flow from the front wing as the different seedings mix. Also, it appears the majority of the flow is exiting the floor before the diffuser, as we discussed earlier, no?



Isn't this one you totally rubbished as not possible because of the position of the exhaust? As I said, getting the geometry right is important.

[ringo]

I rubbished it, because of the pipe position.
But it would be unfair to criticize me since renault are constantly changing the pipe angles and floor airfoil.

Now if you treat me with that level of critcism, you should do the same for the others and their crazy ideas.

Remember you guys went from this

and this:

to this


that is a huge departure.

So you can't act like i made a big change.
All i did was drop the pipe a few cm. Be fair.

My logic is still correct. Regardless of where the pipe is.

The flow goes to the edges of the floor.

Not down the center.

Depending on the speed of the car, the flow will blow either side of the tyre by a range of proportions.

Renault can vary the angle of the floor vane to get differing results

The flow must curl over the top edge

It does not bend 90 degrees


Horse, you cannot say i changed my tune. My logic was constant.
I placed the pipe in different areas and i detailed my observations. They were 100% correct.
I used science, others used hearsay.

Renault exhaust flow is a moving target so no one can say where it blows at any given weekend.
What they can say though is that it does go above the floor as well as bellow. But most of all it blows to the edges.

So I implore you to be objective and show where i made a turn around.