Renault R31

[ringo]

I think Scarbs' explanation is ok as far as it considers approximate position but nothing further than that. No pun intended, just my thoughts.

Orange temperature stickers are glued exactly where he said that the exhaust pipe is pointed out. I think that if that would be the case than whole area would be covered with heat resistant material rather than painted.

What I think is that stickers are glued to a tunnel which no one mentioned. There is clearly a tunel or a pipe, call it whatever you want - a space around the exhaust pipe to enable entrance of air in order to cool the exhaust. Its exit can be seen where sidepods end (boxy shape).

I still claim that exhaust pipe isn't reaching all the way, isn't pointed forward, but bended to blow into several tiny tunels sculptured on top of the floor, which than distribute the gasses below the car to create virtual skirts, and above the floor to generate more downforce as they hit the lip of the floor bent upwards, as well as to aid virtual skirts below the floor as they travel over undercut and floor's longitudinal edge.

You're thinking similarly to what i'm thinking, "air skirts".
The sideways nature of the pipes and the turning vane support the idea more.

The last tests will be interesting if Renault decide to go all out with their ground effect car.

[Blackout]

What do you think of this ? (the carbon piece assembled to the caliper inside of the rim)
And you can see that the brake ducts are tiny

[mith]

I've finally found a video with R31. We can here it there

http://www.youtube.com/watch?v=FnU2GSmisxU

[mx_tifoso]

@ Blackout:

From a number of pages back...

BTW, these calipers seam unusual, as they seam to cover almost 50% of the disc.

[img]http://img534.imageshack.us/img534/5476/new14c.jpg[img]

The calipers are surrounded by cf molding, as per the usual brake system cover but just extended out that far. IMO.

They are coolings ducts which bring air from the drum plenum on the inboard side of the disc out and over the disc onto the outboard side of the caliper.

[Blackout]

Sorry. Thanks. that's explanation for the duct's little size ? Witch cars used it before ?

[mx_tifoso]

No worries.

It's an explanation for the shrouding around the caliper. Which itself might explain why the duct has gotten smaller; an increased internal cooling efficiency requires less air thus allowing for a reduction in drag.

And I don't recall which cars have used this before.

[Formula None]

Edit: D'oh. Long day.

[manchild]

http://www.youtube.com/watch?v=_AXypak4Pe0

Noise noise starts 4:45.

That is R30 not R31

[humble sabot]

Sorry. Thanks. that's explanation for the duct's little size ? Witch cars used it before ?

Renault actually. last year, same size and location.

[steveB]

When Renault said 'radical', could it be that what they have designed is even too radical for the guys on this board to see straight away ?

Rather than the exhaust outlet being designed for aerodynamic flow purposes, could it be that the intention of placing the outlets where they are is to......heat up the track, to give a massive advantage on rear wheel adhesion on low track temperature circuits ?

We have seen the Brawn/Merc cars having problems with this over the last 2 years, and heating up the tarmac using the exhaust would strike me as a rather clever solution?

[jason.parker.86]

If that were the case then the exhausts would be pointed directly at the floor

[Raptor22]

It has energy in the form of speed and temperature. When you impede it's motion or diffuser it the pressure will rise. Naturally it is going to drop to atmospheric after some time outside the pipe, but for example if ones uses their hand to block the pipe and you will see the pressure can get high.

There was a pdf on a CFD analysis of the blown diffuser floating around the internet. the pressure behind the exhaust was higher. I do not know how much higher though, but it can be significant if the exhaust is impeded.

Sorry but thats not correct at. What you are feeling is thepressure rise against your hand not the exhaust pressure. When thehot gas leaves the boundary of the pipe it moves to atmospheric pressure instantaneously. Your hand is feeling pressure due to the velocity of the gas and is not a pressure that will be felt by the underside of the car.

The airflowingunder the car will be accelerated by the faster moving exhaust gas. It is this acceleration of the normal airflow due to the added kinetic energy and thermal energy loss to expansion that accelerates the air flow under the car. That drops the pressure under the car increasing downforce under the stepped bottom.
it is this alone that is doing the magic, nothing else.

Using a exhaust exit in or near the diffusor is slightlyless effective because you impart less kinetic energy to the freestream due to loss of knetic energy due to skin friction. Both concepts allow for accelerating the air flow under the car.

Lotus Renaults solution may have a slightly higher expansion ration resulting a few kilo more downforce but that expansion is now taking place over a much bigger surface area which could negate the benefit.

[horse]

Raptor, could you put that into the other thread as well?

Exhaust Blown Floor - Forward Exhaust Exit

[SLC]

It's 100% an aero benefit.

By increasing the mass flow over the floor LE you end up with a stronger initial suction peak (where the air is accelerated around the allowed 50mm radius coming off of the step plane), and this sets the baseline pressure for the forward half of the floor. This increased strength suction peak will draw in more flow from the T-tray and BBoard lower edges - so in turn you end up strengthening the floor vortex system as well.

It will obviously have an effect on the diffuser and diffuser kink-line performance as well. In general the mass flow under the flow is set by the height of the diffuser exit (and therefore by the pressure recovery the flow experiences), but by artificially introducing more mass flow at the floor inlet you increase the general energy level available for the diffuser kink line to accelerate. Thus, the amount of suction generated by the rear of the floor increases (or, in other words, the more aggressive you are able to make the diffuser kink profile without danger of separation).

There is at some point a balancing act between the load generated by the forward portion of the floor and the rearward portion. The harder you push the floor LE vortex system the more total pressure is lost... leaving the rear of the floor with less energy to work with. This is an on-going battle between front and rear development.

The design aim has nothing to do with heating anything up, either the air or the tyres (or the track surface :p )

Oh and in general, boundary layer buildup on the lower floor surface is not really a big concern. Granted, the increased mass flow effect provided by the forward exhaust will be helping to decrease the adverse pressure gradient along the floor - but seeing as it isn't all that bad in the first place it's not a big deal.

[Blackout]

Sorry. Thanks. that's explanation for the duct's little size ? Witch cars used it before ?

Renault actually. last year, same size and location.

http://farm5.static.flickr.com/4056/471 ... 3b23_z.jpg

I have hundreds of photos of the R30 but not this one or similar. Thanks.
Did they used that solution in many gps?