Exhaust Blown Floor - Forward Exhaust Exit

[shelly]

Ringo

"But what i do know as a fact, is that in both cases, vortex and no vortex, the gases do not go under the floor."

This is another broad statement. May we assume you mean the gases do not flow under the complete floor length? Does not some exhaust have to flow under the front outer corner of the floor to form the vortex?

Brian

sorry I also meant to add this quote in with my last post as what Hardingfv32 says exactly what I mean when I said the vortex would have to pass under the floor to lower the pressure under the floor.

No.

Does a wing tip vortex pass under any floor?

I'll just stand by for now and watch the techno babble unforld. I think there are enough facts already in the thread that readers can draw from.

Due to the pressure difference across its two sides, the bargeboard develops two vortices; the lower one gets squashed under the floor and provides a certain amount of downforce due to its low pressure core acting on the floor surface. cp in the core of this vortex is around -3; it is spinning very fast.

What allison says is that the fee, as the ebd, it is designed to interact with the vortex, strenghten it and lower the pressure in the core. It is not used directly as a jet, but as an twist enhancer for an existing vortex (be it the ebargeboard vortex at the front oor the footplate vortex at the rear). The exhausts get twisted under the floor with this vortex.

So ringo, you are not understanding which is the vortex they are talking about. It is a tip vortex, but it's the vortex that goes under the floor from the tip of the bargeboard.
As I wrote before, if in your model the bargeboard is not working and does not develop the two vortices, you have no chance of seeing this type of interaction.

[marekk]

quite good explanation given already by shelly, so just my 2 cents on this topic:

Wast part of underbody downforce comes from (many) vortice cores interacting with the tarmac facing side of the floor. Due to neagtive pressure gradient along the floor (diffuser &co at work) underbody flows accelerate, resulting in vortices diameter decrease and vortex strenght (downforce) increase. It makes sense to make those vortcies to go along longer paths, which makes them even thinner and stronger (that's what we referenced in our discussion as pushing flowlines to the outside), but it makes definitely no sense to push them all the way out of the floor and into rear tyre - you loose majority of downforce this way.

My interpretation of Allison's description of the system is roughly the same as shelly's - both parties use exhaust to make existing vortices stronger, with renault's added benefit of generating extra downforce directly on airfoil shaped leading edge of the floor (even if not that big as described by ringo - he forgot about much lower then ambient density of exhaust).

I'm still stand by my early ideas - most of the exhaust gases go under the floor and to the rear of the car. I'm not talking about ALL molecules - actually i'm quite sure one can find few of them in front of the car at any given moment.

[ringo]

[quote="shelly"


Due to the pressure difference across its two sides, the bargeboard develops two vortices; the lower one gets squashed under the floor and provides a certain amount of downforce due to its low pressure core acting on the floor surface. cp in the core of this vortex is around -3; it is spinning very fast.

What allison says is that the fee, as the ebd, it is designed to interact with the vortex, strenghten it and lower the pressure in the core. It is not used directly as a jet, but as an twist enhancer for an existing vortex (be it the ebargeboard vortex at the front oor the footplate vortex at the rear). The exhausts get twisted under the floor with this vortex.

So ringo, you are not understanding which is the vortex they are talking about. It is a tip vortex, but it's the vortex that goes under the floor from the tip of the bargeboard.
As I wrote before, if in your model the bargeboard is not working and does not develop the two vortices, you have no chance of seeing this type of interaction.[/quote]

No shelly, you are making things up as you go allong.
Allisons said nothing like that.

I asked if in the case of a rear wing end plate, does it need any kind of floor to form a vortex.
It does not, we see vortices coming off wings all the time.

I think you have a misunderstanding of what the vortex is, how the floor works and are trying to bend things so it fits you beliefs.

Here is the vortex:
Not the best of representations, as the pipe angle and height are wrong, but a vortex doesn't need to be under anything to form.


I'll repeat: You don't want any air coming under the sides.

[shelly]

ringo, I am not doing anything of what you are writing. Instead of putting out accusations, why don't you ask what it's not clear for you in my post?

It seems to me that you have not still understood which voretx I am talking about, as you keep showing another one

[machin]

the bargeboard develops two vortices; the lower one gets squashed under the floor and provides a certain amount of downforce due to its low pressure core acting on the floor surface

Are you saying that with a properly designed bargeboard we would expect to see a low pressure "plume" on the underside of the floor? See my "MS paint mark-up" below???

[ringo]

I've done a test again.
This time with a more accurate to R31 leading edge and gurney and pipe.


This is not all the flow lines there are more, but it's quite a mess. I'll show the rest when i get home.



The vortex is formed in both cases and you can see the similarity bewteen the reality and the cfd.

The vortex makes the skirt taller, which helps. This is why the dust clouds are so high it seems.

[ringo]

ringo, I am not doing anything of what you are writing. Instead of putting out accusations, why don't you ask what it's not clear for you in my post?

It seems to me that you have not still understood which voretx I am talking about, as you keep showing another one

Shelly as said before, it's best you draw diagrams. Words don't best represent what you are trying to say if they can be changed in following posts. Its hard to follow.

The vortex has to be normal to the edge that it's swirling around. It aslo needs room to form the circle.
Ground effect prevents vortices becuase there is no room for them to form. So there is really no such thing as an under floor vortex. Not enough room to swirl under there.
You follow what i mean?

[raymondu999]

Slightly OT here; but you seem to have designed a side pod concept half towards the McLaren concept; and kind of like the one on an F1 racing mag a while back; care to explain why?

[shelly]

the bargeboard develops two vortices; the lower one gets squashed under the floor and provides a certain amount of downforce due to its low pressure core acting on the floor surface

Are you saying that with a properly designed bargeboard we would expect to see a low pressure "plume" on the underside of the floor? See my "MS paint mark-up" below???

yes exactly. But it will be a lot shorter than in your sketch - some 30 to 50 cm

[ringo]

Slightly OT here; but you seem to have designed a side pod concept half towards the McLaren concept; and kind of like the one on an F1 racing mag a while back; care to explain why?

Oh that was experimental. This is Machin's car, but it is modified to investigate any little novelties that are found in F1.

The sidepods were done to see the benefit of the L cut

[strad]

I'll repeat: You don't want any air coming under the sides.

YES YES YES,,,You've got it.IMO...and as much as one usually doesn't want vortexes,,,they in this case can be used to form a roll of air at the edge to act as a cushion...Is that not correct Ringo?

[wesley123]

@Ringo; seems likely the flow will go like that, I would say this just creates a seal, it stops air flowing in from the sides.

I orriginally thought that with the flick up it would create a powerful vortex on the floors edge, doing effectively th same thing.

[MIKEY_!]

How legal would a kind of slit exhaust (like that on the mclaren during testing) be when mounted on the splitter. What are the rules regarding holes on the top of the splitter???

[jordangp]

There were some Thermal Images of the Renault's FEE in the pits in Practice 1 this morning, hopefully they may be of some use

[marekk]

What do you think about relative paths of solid (sparks) and gaseous (flames) particles on this photo.

I'm the only one to see the flow going under the floor and exiting inside rear tyre ?