Exhaust Blown Floor - Forward Exhaust Exit

[Sonic59]

2) "No. The vortex is working like a skirt. It prevents air from outside of the car to move under its body. If air moves under body it spoils low pressure zone:"

James Allison is the Techincal Director of Lotus Renault. Are we to believe you or anyone on this forum have a better understanding of this subject than him?

Brian

The vortex can not be a reason to create downforce cause u need vertical flow momentum to create it. What Allison (whom I respect a lot) said is correct if u understand his words in a right way.

[shelly]

And how does this low pressure vortex generates its dfownfore then? Right, by blowing it under the flow, it actually seals the floor.

It does not need to seal the floor to generate downforce.
The low pressure vortex generates downforce simply because it is low pressure and it blows under the floor. The was a good picture in the previous pages of this thread.

[MIKEY_!]

I think you would have to get the centre of the vortex in contact with the under side of the floor for that to work?

[shelly]

yes that is how it works -no "would". Low pressure vortex core in contact with the underfloor.

[MIKEY_!]

But if the core is in contact with the floor won't the vortex walls be disrupted as they hit the floor and the vortex will break up?

[shelly]

Nope

[Sonic59]

yes that is how it works -no "would". Low pressure vortex core in contact with the underfloor.

Are u able to explain why votex has low pressure?

[shelly]

The air particles follow a tightly curved helica path along the vortex , so a preesure gradient develops as a consequence (or it can be seen as the force providing the centripetal acceleration. Or in other words, because of radial momentum consevation, you can not have a vortex type trajectory fo the flow without a low prssure core "holding" the particles along that trajectories.

Seeing your posts sonic I think you knew the answer already before posting the question

[Sonic59]

The air particles follow a tightly curved helica path along the vortex , so a preesure gradient develops as a consequence (or it can be seen as the force providing the centripetal acceleration. Or in other words, because of radial momentum consevation, you can not have a vortex type trajectory fo the flow without a low prssure core "holding" the particles along that trajectories.

Seeing your posts sonic I think you knew the answer already before posting the question

So it means than the reason of the pressure drop in vortex is rotation. Right? Then if we calculate rotational energy we can measure flow energy loss. If we have enrgy loss we can get pressure drop. If we have pressure drop - we can measure downforce gain. Try to make the calculation by yourself.

[shelly]

Are you looking for an integral of the Rankine formula in the core?

[hardingfv32]

"I'm quite sure the kink is not the start. the "start" is all the way at the front of the floor. "

Just trying to establish some commonly defined terms. The rules seem to imply that the kink is the start of the diffuser by the dimensions that are specified.

Brian

[hardingfv32]

"Of course Allison will reveal everything about the system. What has he actually said about the exhaust usage? Right that it generates a vortex which creates downforce. Where it does is not said, but with the footplate of the diffuser being covered i metal I find it quite clear this vortex goes under the floor, sealing the floor from the rear wheels."

Allison clearly states the vortex being formed creates low pressure. This low pressure is used to produce downforce. There is no mention of sealing. I am not sure we have ever heard a current F1 engineer state that there is a sealing effect. We also have not seen any CFD work illustrating this sealing.

Brian

[hardingfv32]

Using the vortex's low pressure at the edge of the diffuser......

Exactly how is the vortex placed in relation to the edge of the diffuser? Consider the side of the diffuser to be a flat plate or blade with a straight edge. The vortex has a traditional circular shape.

Brian

[wesley123]

"Of course Allison will reveal everything about the system. What has he actually said about the exhaust usage? Right that it generates a vortex which creates downforce. Where it does is not said, but with the footplate of the diffuser being covered i metal I find it quite clear this vortex goes under the floor, sealing the floor from the rear wheels."

Allison clearly states the vortex being formed creates low pressure. This low pressure is used to produce downforce. There is no mention of sealing. I am not sure we have ever heard a current F1 engineer state that there is a sealing effect. We also have not seen any CFD work illustrating this sealing.

Brian

ringo has done some CFD on the FEE actually showing a bit of the sealing effect. Apart from that, the metal plating gives it away doesnt it? Sure if the flow doesnt go there, why put metal plating there?

[godlameroso]

The metal is obviously there to protect the carbon diffuser. However, the vortex runs across the width of the diffuser, the one from each exhaust, and one from the beam wing, all converge at the extreme rear of the car. Each one influencing and "egging each other on" so to speak. Remember the car works as a whole, so you have these vortex of low pressure helping streamline all the air that spills over the front half of the car. If by "sealing" you mean that flow retards in separating then yes, it does have a "sealing" effect