Exhaust Blown Floor - Forward Exhaust Exit

[BreezyRacer]

I appreciate all the effort going into this but we're kidding ourselves to think that what you guys have worked to do is what is actually going on .. until you get some true flows from the real design (never gonna happen) we can only prod our way thru what we find.

Myself, I think the flow is going mostly under the car, not onto the top of the tray, creating a low pressure area under the car by sealing off airflow under the car. But what the hell do I know?

When I've done this in the past you would "grow" your way to a solution .. test this then test that, all the while observing what is happening vs what you wished happened. Eventually you get to a happy place or discard the idea. These guys built a car around this idea and that alone tells me it works ..

Last year Renault were a surprise. They had fresh aero ideas and worked at a relentless pace to bring them to the track all thru the season. Vastly different from what we came to expect from Briatore. And they all worked as designed right out of the box, just like Newey's work, maybe better (Newey had to redesign his Fduct but then he was two races earlier than Renault too).

I think we might even be experiencing the next Newey working now at Renault, driving these interesting ideas .. Renault ain't no stick in the mud anymore ..

[hollus]

Another thought on the hot exhaust air going under the car (which we are not sure it does) and cooling down there (we know that even less):
What is the exhausts' water content after burning the fuel? It it cools enough, would it be reasonable to expect that moisture to start condensing into water, further reducing the volume of the gas and the pressure under the floor? Probably not, the car passes under that air way too fast, I guess.
But if it does, it should be visible as a plume coming out of the sides or out of the diffuser, that is, in a very very humid day.

[segedunum]

Exhaust gas is not going under the car. As xpensive has pointed out earlier in this thread you definitely don't want density to go down. If you have trouble thinking about this just think of what you learned at school about hot air rising. You don't want hot air underneath something that you want to keep on the ground.

What they are probably doing is routing the hot gas around the sides of the car to speed up flow around it (see earlier in the thread), but that hot gas is cooling so quickly it's difficult to see what kind of effect they are getting from it versus the effort they're putting in and the diffuser approach teams like Red Bull are taking.

[forty-two]

Seg, while I am far from qualified in this field, I think it might pay you to read some posts from SLC earlier in this thread where he beatifully explains a number of things which are contrary to your views. I know that we can only go on SLC's opinions on this, but to be fair, he has been spot on in the past.

[marekk]

No idea about downforce, but i'm pretty sure, that with hotter (and less dense) air you get lower drag (skin friction, induced drag ...) - maybe that's renault's point ?

[xpensive]

An interesting point marekk, aerodynamic drag is obviously proportional to density, when dynamic pressure being rho*speed^2/2. Didn't see that one coming, but if so why not route the xhaust to the tip of the nosecone or something?

As for the gasses quickly cooling off, the animations above are cute, but I don't think we should take them to the bank, at full song there's more than 250 kW(think 500 Sunday morning toasters) spewing out from each pipe at a speed much higher than the car itself. What were the input numbers in those images anyway?

Edit: Thanks marekk, these are more likely numbers.

[speedsense]

No idea about downforce, but i'm pretty sure, that with hotter (and less dense) air you get lower drag (skin friction, induced drag ...) - maybe that's renault's point ?

Scooping the side pods and adding hot exhaust as sealing measures for the sides of the floor...can't be wrong can it? Physically sealing the sides of the floor is against the rules, the next best thing? Block the intervention of the front wings and wheel "air pumps", IMHO

On two occasions, with two different drivers, the Renault has been fast.... IMHO, I don't think this will be the only car with front side pod extracting exhausts. How many exhaust systems has Mclaren used so far?

[tok-tokkie]

The motor is 650kW is it not? 30% as mechanical energy, 35% to cooling & 35% out the exhaust? And KERS will be taking a little from the exhaust.

I am very interested in the heating of the ambient local air by the rejected heat as I believe the McLaren will have an advantage when slipstreaming through the placement of their radiators not resulting in the same engine cooling problems as the others experience (an airflow effect, not ambient air temp effect). Will the FEE make the Renault easier to slipstream without overheating? I don't expect it will.

[segedunum]

Seg, while I am far from qualified in this field, I think it might pay you to read some posts from SLC earlier in this thread where he beatifully explains a number of things which are contrary to your views.

It's entirely possible. All we can do at the moment is speculate because Renault will have done some major analysis on all the variables in this that we don't have.

If they really can create a ground effect with this in the middle of the car then it really will be worth something and will be a major area of development because this is an area of the car that has not generated downforce since the early eighties. I don't think this is about conditioning the air to the diffuser to be honest. For me, the effect could well be lost long before the air gets there....but then these are very hot gases being expelled at extremely high speed. To summarise, I would concentrate on using this to create a ground effect rather than doing things with the air forward of the diffuser. Expect to see strangely sculpted sidepods and sidefloors in future if this is the case.

If this is what Renault are doing, and it works, then they've really got something.

[marekk]

The motor is 650kW is it not? 30% as mechanical energy, 35% to cooling & 35% out the exhaust? And KERS will be taking a little from the exhaust.

I am very interested in the heating of the ambient local air by the rejected heat as I believe the McLaren will have an advantage when slipstreaming through the placement of their radiators not resulting in the same engine cooling problems as the others experience (an airflow effect, not ambient air temp effect). Will the FEE make the Renault easier to slipstream without overheating? I don't expect it will.

650kW it's just mechanical part, as mesured on the dyno. We are speaking another 1400kW to radiators and exhaust. And KERS gets his energy from breaking, not from exhaust. If you can use part of this energy to reduce drag, you can run more wings, bigger sidepods, additional colling inlets ...
All of those features we see on R31.

[Paul]

Does anyone know if there were ever experiments on race cars where the floor was deliberately heated to energise the flow and gain downforce? For example, I could imagine flat panel heat exchagers like the ones tried on Brabham BT46 installed in place of bare floor panels, thus also contributing to engine cooling. But that is just my imagination, so...

[JaymzVsTheWorld]

Does anyone know if there were ever experiments on race cars where the floor was deliberately heated to energise the flow and gain downforce? For example, I could imagine flat panel heat exchagers like the ones tried on Brabham BT46 installed in place of bare floor panels, thus also contributing to engine cooling. But that is just my imagination, so...

I remember a few years ago I hear a roumour about the bodywork having an electric current flowing over it, I think it was Ferrari that tried it out, or so I heard.

[marekk]

Does anyone know if there were ever experiments on race cars where the floor was deliberately heated to energise the flow and gain downforce? For example, I could imagine flat panel heat exchagers like the ones tried on Brabham BT46 installed in place of bare floor panels, thus also contributing to engine cooling. But that is just my imagination, so...

I remember a few years ago I hear a roumour about the bodywork having an electric current flowing over it, I think it was Ferrari that tried it out, or so I heard.

And this year almost all of the cars are equiped with more or less reliable sorce of high voltage current (KERS). In the aviation there are some planes, which use controll boundary layer separation by some plasma injection devices near leading edge of airfoils.

[BreezyRacer]

Sheet 7 of this thread has some interesting images showing dynamic ride heights amongst the teams. Renault is is lowest by a good margin. It is consistent with the idea that they are running lower heights to make the exhaust block off the sidepod inlets to create, essentially a massive low pressure under the car, starting at the front of the sidepods. Just speculation of course , but there you go ..

viewtopic.php?f=1&t=9465&start=90

Ya see what ya want to see and ya hear what ya want to hear ..

[tok-tokkie]

The motor is 650kW is it not? 30% as mechanical energy, 35% to cooling & 35% out the exhaust? And KERS will be taking a little from the exhaust.

I am very interested in the heating of the ambient local air by the rejected heat as I believe the McLaren will have an advantage when slipstreaming through the placement of their radiators not resulting in the same engine cooling problems as the others experience (an airflow effect, not ambient air temp effect). Will the FEE make the Renault easier to slipstream without overheating? I don't expect it will.

650kW it's just mechanical part, as mesured on the dyno. We are speaking another 1400kW to radiators and exhaust. And KERS gets his energy from breaking, not from exhaust. If you can use part of this energy to reduce drag, you can run more wings, bigger sidepods, additional colling inlets ...
All of those features we see on R31.

Thanks.