Red Bull RB8 Renault

[Pup]

The EBD isn't the only setback RB have had, though. There are also stricter restrictions on the front wing which I suspect may have been a bigger advantage for them. And then there's the new off-throttle restrictions, which not only reduce the effectiveness of the EBD, but may also have reduced their fuel advantage since the other teams aren't wasting fuel by hot-blowing.

[munudeges]

So are Red Bull paying the price of not putting this exhaust solution on their car from launch?

Most probably. This thing needs track time to get it to work properly.

[Shakeman]

So are Red Bull paying the price of not putting this exhaust solution on their car from launch?

Most probably. This thing needs track time to get it to work properly.

Can you define what working properly means?

I'm still not clear on what the teams are trying to achieve and when they get it to work properly what exactly is happening and what performance increase it is giving them.

[Crucial_Xtreme]

So are Red Bull paying the price of not putting this exhaust solution on their car from launch?

Most probably. This thing needs track time to get it to work properly.

Can you define what working properly means?

I'm still not clear on what the teams are trying to achieve and when they get it to work properly what exactly is happening and what performance increase it is giving them.

Look on the previous page & read my post.

Red Bull is trying to get the airflow to come down to the lower corner of the bodywork and get involved with setting up a vortex to seal the floor. But simulating it with mass flow of exhaust, as well as mass flow of the whole car, is very difficult. You need to play with temperature sensors on the bodywork to see where the hot part of the flow is going before channelling it where you want. The Coke Bottle will not be as effective because of the blockage of the exhaust. Part of what the Coke Bottle does is drag airflow inward that would otherwise go under the floor, so with the exhaust in the way you need to help prevent that flow from going under the floor. The hole you see here creates a bigger low pressure area, allowing the flow to be pulled towards it rather than below the floor. To get the pulsing exhaust flow working(it's not just a constant flow) during simulation is very difficult. Circuit testing is really the only way to do it. This layout may be as a result of what Red Bull found from the heat sensors.

[Shakeman]

[quote="Crucial_Xtreme"

Look on the previous page & read my post.

Red Bull is trying to get the airflow to come down to the lower corner of the bodywork and get involved with setting up a vortex to seal the floor.[/quote]

I am having trouble buying the "sealing" of the diffuser with the exhaust gases so much further away. Isn't it just a case of trying to get any hot air they can under the floor by the rear wheels.

I've not seen any of these technical analysts give any indication what performance is to be gained by the limited ability left to blow the diffuser and a conventional exhaust position.

I guess what I'm ying to get an idea of is whether the teams are going to continue to develop the exhaust/diffuser or look to other areas of development as they offer greater performance steps.

[Crucial_Xtreme]

I am having trouble buying the "sealing" of the diffuser with the exhaust gases so much further away. Isn't it just a case of trying to get any hot air they can under the floor by the rear wheels.

I've not seen any of these technical analysts give any indication what performance is to be gained by the limited ability left to blow the diffuser and a conventional exhaust position.

I guess what I'm ying to get an idea of is whether the teams are going to continue to develop the exhaust/diffuser or look to other areas of development as they offer greater performance steps.

Well this is exactly what they're trying to do, and at a minimum McLaren is accomplishing it.

CFD from n smikle
viewtopic.php?f=6&t=12046&p=314877#p314877

Technical Analysis from Scarbs



Teams have sought to keep the exhaust floor pointed at this crucial region between the rear tyre and the diffuser. However the new exhaust rules preclude any exhaust position that would directly aim the plume to this region.

This is where the downwash sidepod design comes into the equation. Although the exhaust plume is at great speed and exits with a lot of energy, it can still be affected by the general flow over the car. As speed increases the cross flow passing over the exhaust pipe, will bend the exhaust plume into a curve.

Teams have realised that this can be used along with other aerodynamic effects to make the exhaust plume move from an upwards direction to downwards, towards the sides of the diffuser. The trick in achieving this is to create a strong downwash of airflow over the sidepod. Several teams have gone this route: McLaren, Sauber and latterly Red Bull with the new aero package released over the weekend at the final Barcelona test. Other teams like Ferrari and Mercedes use a similar effect for different reasons.
At speed the downwash (yellow) over the sidepods deflected the exhaust (red) towards the floor
At speed the downwash (yellow) over the Sauber sidepods deflected the exhaust (red) towards the floor (Click picture to enlarge)

Downwash sidepods work by the high pressure created above the chassis and sidepod fronts being directed by the sloping top surface of the sidepod towards the exhaust outlet. Directing this flow over the exhaust creates the bending effect of the exhaust plume. Then detail work with small vanes and brake duct vanes help to keep the plume pointed at the edge of the diffuser and the tyre itself.

Conclusion

As the season progresses teams will constantly play with the sidepod and exhaust shape. Many midfield teams have opted for a non-sensitive exhaust position, with plans to exploit the exhaust gasses once the effect is better understood. The downwash sidepod and exhaust is clearly a key performance differentiator between the teams this year.

Link--> http://plus.autosport.com/premium/featu ... -to-speed/


The teams are definitely trying to get the exhaust gasses to the edge of the diffuser with the intent on sealing it much like 2011. RB changing it's exhaust in Barcelona to the same type solution they have now is confirmation of just that. otherwise why move them from way inboard to as far outboard as possible? Add they have been trying different ones is more evidence.

Teams whos exhaust is working like they want, McLaren, Sauber, etc will focus on other things most likely. Whereas teams like RB & Ferrari will work on the exhaust until they get them right. The performance is obviously worth it to the teams.

[raymondu999]

Let's say it does really do the sealing. How exactly are they going to set the car up? I mean; the benefit of sealing the diffuser, in very generalised terms is so that you can run a higher rake angle. But if you then take away this sealing effect, the diffuser will not work at that higher rake angle, no?

So do you then set up the car with an amount of rake that it achieves when the driver is off the throttle, or do you set it up for the amount of rake you can get when the exhaust is helping the sealing? With the disappearance of Off-throttle mappings; the exhaust flow will be throttle sensitive.

[Crucial_Xtreme]

Let's say it does really do the sealing. How exactly are they going to set the car up? I mean; the benefit of sealing the diffuser, in very generalised terms is so that you can run a higher rake angle. But if you then take away this sealing effect, the diffuser will not work at that higher rake angle, no?

So do you then set up the car with an amount of rake that it achieves when the driver is off the throttle, or do you set it up for the amount of rake you can get when the exhaust is helping the sealing? With the disappearance of Off-throttle mappings; the exhaust flow will be throttle sensitive.

I think it's trial & error. Considering we've only had one dry race on a non conventional track, the teams probably aren't 100% on the best setup. It's probably the middle ground of the two options you posted above?

[raymondu999]

You'd be in a very good position 85% of the time and in a compromised position the other 15% though (random figures on average amount of throttle use through a lap)

[Shakeman]

When we're talking of sealing the diffuser are we saying that the effective width of the diffuser is extended to the inner side of the rear wheels or are we saying the hot gasses "seal" the diffuser from the floor down to the ground?

I can see the former example working in the CFD plots.

[raymondu999]

We're saying that the exhaust flow forms a "wall" to the left and right of the diffuser; physically sealing in gases that would have escaped at higher rake angles.

[Shakeman]

We're saying that the exhaust flow forms a "wall" to the left and right of the diffuser; physically sealing in gases that would have escaped at higher rake angles.

Right, that's what I thought and I'm having trouble seeing on any CFD. Last year was no stretch to the imagination at all with a focussed exhaust.

At what point does it become a seal rather than just energised gases flowing through the diffuser?

[hardingfv32]

At what point does it become a seal rather than just energized gases flowing through the diffuser?

This has been discussed before on the forum and there is no consensus about how the diffuser would be sealed.

a) An air flow type screen as discussed above or,

b) A vortex generated at the gap between the diffuser and the tire which adds low pressure to the underside of the diffuser. This is an idea that was stated by Lotus's Technical Director.

Your not going to see it on any CFD unless it is correctly detailed in the region of the gap. I would say the theme was refine last season using the very precisely aimed exhaust flow. These flow were very narrow and concentrated and not affected by exterior flows. That is not the case this season. While you might get the exhaust flow aimed at the this gap this season, it is not narrow, concentrated OR unaffected by the exterior flow. This year it is more a case that a little of some thing is better than nothing.

Brian.

[Crucial_Xtreme]

Right, that's what I thought and I'm having trouble seeing on any CFD. Last year was no stretch to the imagination at all with a focussed exhaust.

At what point does it become a seal rather than just energised gases flowing through the diffuser?

I'm not sure why you're having trouble.





I understand this is the MP4-27, but it is exactly what Red Bull are trying to accomplish.

[godlameroso]

The sealing you speak of has something(not all) to do with the heat generated, and something smaller still with the energy of the exhaust, and how it affects the relatively cooler airflow around it. In other words it's easier to generate low pressure if you have a stream of hot air with cooler air circulating it. The diffuser and body work already create a vortex to begin with, and by injecting a stream of hot energized air through the center of that vortex, you will invariably magnify the pressure differentials caused by said vortex.

It's the difference between this
[youtube]http://www.youtube.com/watch?v=4b2SV3ASUxY[/youtube]

and this;
[youtube]http://www.youtube.com/watch?v=IyAyd4WnvhU[/youtube]

of course it's a little exaggerated but the point is no less valid...if there is one.