Exhaust Blown Floor - Forward Exhaust Exit

[ringo]

I might have some cfd up comparing with and without the front exhaust.
It's hard to say now what it's really doing. Depending on the angle it can blow to the edge of the floor, or in a little bit more and depending on how it's split top to bottom can actually flow around the side pods and through the gap between the wheels.
It definitely blows into the tyres, but it stays low to the ground near the contact patch area.
temp seem to be a 20 degree increase at the tyres assuming the exhaust comes out at 800*C

Thanks to machin for his 2009 car.


not the best looking interpretation, but it's close enough. It's a 2.5 inch pipe. I added a little airfoil on the edge of the floor.



flow paths with temperature scale. Flow from exhaust and the lumpy airfoil end of the floor.
The exhaust doesn't create much vortices, not more than the airfoil shape on the floor tip.
I tried it with no airfoil and there were no swirls. Edges and pressure difference are required for that.
gases cool rapidly, the scale is between 400Kelvin and abient just to give a nice colour contrast. If it were at the ex temp of 1073K you'd see mainly just blue showing how quickly the gas cools from 800 to around 20 degrees above ambient.


from underneath, this time with velocity scale. car is moving at 70m/s. So was the floor which is hidden here.


from the back.

Blowing that airfoil seems to be the main purpose. The side effects i am not sure. Looks like an increased effort to seal the floor, which the air foil can do by itself. Or maybe something to do with the flow between the wheels?

Hard to come to any conclusion since i don't have any downforce number yet. Also need to make a good comparison without the FEE.

[PlatinumZealot]

show a cutplot of in a transverse plane along different lengths of the floor. So we can see the vortices on the floor edges.

[horse]

Aren't these pipes too far out of the chassis?



Also looks like the exhaust is exiting completely above the floor, whereas it looks like it would split at the cut out in the Renault floor.

Set it up so it goes under the floor, Ringo. See what it does in that case too.

EDIT: Pitot tube array on the rear wheel of the R31, Ringo. You might be on to something here!

Further to that, do you think that the exhaust gases hitting the rear wheel, say, rather than theories a) or b) would be useful? Could it increase the pressure differential across the rear wheel and thus give more "suck" to the diffuser?

[forty-two]

Breathtaking bit of work there Ringo! Well done.

My theory is that at lower speeds the exhaust gases go mostly toward aiding downforce, but when at higher speeds, the higher speed of draught pushes the fumes under the car where they can help the diffusor out but don't have such a sealing effect for the floor.

I believe that this is the reason why the exhaust is not angled directly backwards, but instead it exits at about 45 degrees.

[PNSD]

Nice work Ringo, but ive never been convinced by the accuracy of Floworks/COSMOS or whatever name it goes by. I cant remember hearing anything good so im not too sure how accurate it would be in simulating a high velocity exhaust plume and how it interacts with the overal flow field of the car.

[ringo]

Aren't these pipes too far out of the chassis?

Well it had to be this way for this car, since it's not the same shape side pods or vertical turning vane as the renault. If you notice on the renault there is a clear view through the turning vane to the exhuast. I tried to achieve that with the angle of this pipe.

Also looks like the exhaust is exiting completely above the floor, whereas it looks like it would split at the cut out in the Renault floor.

Set it up so it goes under the floor, Ringo. See what it does in that case too.

Half of it is actually under the floor. I might put more of it below, but i suspect it still wont make a full 90 degree turn and go straight under. I also suspect that at lower speeds it will shoot out more to the sides.

Further to that, do you think that the exhaust gases hitting the rear wheel, say, rather than theories a) or b) would be useful? Could it increase the pressure differential across the rear wheel and thus give more "suck" to the diffuser?

[/quote]

I think it's partially going over the floor between the wheels. I don't know if there is a benefit to hitting the wheels, but these have to do with it:

That scoop in front of the wheel.

I can add them, but to tell the truth you have to know exactly what you are trying to achieve if you are to fully understand what's happening here.

What i will do is compare blowing to not blowing. Both the under floor views and above floor.
Then look on a lower speed.

[ringo]

Nice work Ringo, but ive never been convinced by the accuracy of Floworks/COSMOS or whatever name it goes by. I cant remember hearing anything good so im not too sure how accurate it would be in simulating a high velocity exhaust plume and how it interacts with the overal flow field of the car.

It's as accurate as your computer can manage. It will simulate very well, it's only bad at actually giving direct values like downforce etc. It's really better for internal flow.
I don't have a super computer or super exclusive software like the F1 teams but I'm sure it's more accurate than the speculation in the thread.

[flynfrog]

nice work ringo

As for the accuracy who cares its still going to be pretty close. We only care about colorful fluid dynamics anyway pretty pictures.

[747heavy]

front exiting exhaust, flow/blow over the floor?

as seen in DTM cars in 2006?
Took F1 a while to catch up ! - just kidding

[ringo]

Well they might take a while to put a windscreen on the cars too!
leaders in motorsport



temp sensors in the same area indicated by the flow?


on to something here

[PNSD]

Nice work Ringo, but ive never been convinced by the accuracy of Floworks/COSMOS or whatever name it goes by. I cant remember hearing anything good so im not too sure how accurate it would be in simulating a high velocity exhaust plume and how it interacts with the overal flow field of the car.

It's as accurate as your computer can manage. It will simulate very well, it's only bad at actually giving direct values like downforce etc. It's really better for internal flow.
I don't have a super computer or super exclusive software like the F1 teams but I'm sure it's more accurate than the speculation in the thread.

Touche! We do the best with what we got!

Flynfrog, ive always been taught its colourful fluid dynamics rather than computational

[forty-two]

Anyone know if the reports that McLaren were seen using a FEE today have any basis?

http://www.f1sa.com/index.php?option=co ... Itemid=157

[Blackout]

http://www.f1fanatic.co.uk/wp-content/u ... e_2011.jpg

temp sensors in the same area indicated by the flow?
http://i1010.photobucket.com/albums/af2 ... xhaust.jpg

on to something here

And

[machin]

Ringo, nice work there... good to see my model being put to some actual use. =D> (looks like you'ev put the wheels in the wrong place though -too far forward?)

Can your analysis software do surface pressures? Afterall flow lines look nice, but at the end of the day all we really care about are pressures on the car....

If anyone wants to see the original CFD analysis on the standard car (with a basic 2009 double diffuser) I posted the pics here:-

viewtopic.php?f=6&t=6770&start=105

[csponton]

In search of the lost downforce

http://spontoncristiano.wordpress.com

EXHAUST RENAULT

PRO

In an attempt to recover the lost downforce at the rear, Renault's engineers have decided to speed 'exhaust gas to speed the flow of air flowing under the car. It 'an extreme example of low discharges, but the blow follows the entire length of the bellies up to the speaker.

V
To exploit this principle must use a non-ideal configuration for an exhaust system: they are too long lose power even if you have maximum benefit in terms of torque. Very gentle even passing pipes red hot (about 700 degrees) within the distance of the sides that could create problems.

DOUBLE BOTTOM TORO ROSSO

PRO
The solution developed by Ascanelli follows the concept introduced in 1992 by Jean Claude Migeot with Ferrari. The sides, instead of going to connect with the bottom shell in the back, are raised for their entire length. This will create an additional channel between the bottom and the bottom of the side pods which should increase the downforce.

V
We must verify in practice whether the level of downforce is constant or subject to rapid changes. If so, the leader, become 'very difficult with a velocity' greatest little exciting. All of these problems, the Ferrari of 92 had them. Let's see if this concept, applied aerodynamics today, you may 'work.

Rear WILLIAMS

PRO
The rear on the FW33 and 'very low, remained behind bars twist and change and' small. The triangles above the rear suspension is anchored to the support wing. The differential 'was positioned very low to create a channel of airflow to the wing pisteriore. All this to try to recover downforce on the rear and lower the center of gravity of the car to make it more balanced.

V
Collec the differential down means taking the corner cengeniale not for the better functioning of the axle shafts. This may create problems of overheating. While securing the rear suspension to the wing pylon is not 'the ultimate in rigidity' structure. Especially in the fast corners there may be problems of stability.

Next to "L" McLAREN

PRO
The Mclaren and 'the only one to have bellies that have grossed a deep trench between body and air vents that serves to channel the air towards the rear. To do this, the radiators in the flanks, have been relocated.

V
The evidence in the wind tunnel of this solution are not very encouraging. All the other top teams (Red Bull, Ferrari, Lotus-Renault) have slim and sleek while the rear of the Mclaren and 'very cumbersome. The interaction with the new releases (although style Lotus Renault should not blow under the body) and 'to be verified in particular that the internal temperature of KERS and' put in the same area.