Diffuser functions

[bot6]

Another advantage is that a higher rear end artificially adds volume to the diffuser, hence makes it "think" it's bigger than it really is. With the cannon exhausts on the side acting a bit like side fences and enclosing the volume of the diffuser more efficiently, you lose the disadvantage of more air rushing in the diffuser through its sides. So the conjunction of a higher rear end plus the cannon exhausts will bring a real performance enhancement to the diffuser. It's all working together as an integrated package.

[Lindz]

Another advantage is that a higher rear end artificially adds volume to the diffuser, hence makes it "think" it's bigger than it really is. With the cannon exhausts on the side acting a bit like side fences and enclosing the volume of the diffuser more efficiently, you lose the disadvantage of more air rushing in the diffuser through its sides. So the conjunction of a higher rear end plus the cannon exhausts will bring a real performance enhancement to the diffuser. It's all working together as an integrated package.

Yes, very true (and smart about the Red Bull rear end).

But also remember that the efficiency of the diffuser will be lower with a higher rear end since the percentage of air it is able to effect (change of pressure) will be less.

[marekk]

Another advantage is that a higher rear end artificially adds volume to the diffuser, hence makes it "think" it's bigger than it really is. With the cannon exhausts on the side acting a bit like side fences and enclosing the volume of the diffuser more efficiently, you lose the disadvantage of more air rushing in the diffuser through its sides. So the conjunction of a higher rear end plus the cannon exhausts will bring a real performance enhancement to the diffuser. It's all working together as an integrated package.

+1.

Basically more rake = more angle of attack on all 3 main downforce generating surfaces (diffuser, floor, front wing) = more downforce.
But make it a bit to much, and it will stall (first of all diff), loosing at a sudden big part of this downforce.
So you have to speed up the flows to help keep it attached - by sealing the sides (cannon exhaust), directing some of the high energy gases to main diff sector, blowing as much of fresh air on diff gurney and lower wing (packaging).
It works only as a package, there is no easy way to get it right by just copying one or two bits.

[bot6]

But also remember that the efficiency of the diffuser will be lower with a higher rear end since the percentage of air it is able to effect (change of pressure) will be less.

I don't quite get what you mean here. Care to elaborate a little bit?

[PlatinumZealot]

Another advantage is that a higher rear end artificially adds volume to the diffuser, hence makes it "think" it's bigger than it really is. With the cannon exhausts on the side acting a bit like side fences and enclosing the volume of the diffuser more efficiently, you lose the disadvantage of more air rushing in the diffuser through its sides. So the conjunction of a higher rear end plus the cannon exhausts will bring a real performance enhancement to the diffuser. It's all working together as an integrated package.

Yes, very true (and smart about the Red Bull rear end).

But also remember that the efficiency of the diffuser will be lower with a higher rear end since the percentage of air it is able to effect (change of pressure) will be less.

No. You get more downforce up to a certain rake angle. This is becuase the whole floor will act like a diffuser. Also, adding rake makes up for the growing boundary layer as the roughness of the floor slows the air down as it passes along. So rake is good. That is why RedBull have so much.

[Lindz]

But also remember that the efficiency of the diffuser will be lower with a higher rear end since the percentage of air it is able to effect (change of pressure) will be less.

I don't quite get what you mean here. Care to elaborate a little bit?

I wrote a response and even drew a diagram, but what we are dealing with is WAY more complex than what my statement implied.

I don't mean to say that the RB7 diffuser is not efficient. In fact, if it is designed around a high-rake floor, it may well be MORE efficient at creating overall pressure change and downforce from the floor.

In isolation, the diffuser produces downforce by creating suction from a change in pressure in the volume of air that passes through it. That volume of air passing through the diffuser will not change, but the overall volume of air under the car will be greater with a higher rear floor. Therefore, the volume of air the diffuser is affecting (by itself) is a smaller percentage of the under-floor air.

However, it's stupid of me to imply that it's solely the diffuser that matters. Perhaps the diffuser alone is creating a smaller percentage of the rear downforce, but a raked floor also changes the pressure from front to rear. So now your flat floor is actually producing downforce as well. Feed it with exhaust flow to 'fence' the diffuser and add energy and speed to the air and this also gives you more efficiency.

Every part needs to be looked at as a whole concept, not individual pieces. And it's the sum of all parts that make the RB7 a great car.

[horse]

Anyone thought, that if the rear ride height is determining the rake, then the leading edge of the floor must also be higher than on the other cars?

To elaborate, if the roll hoop is higher (as in the comparison pictures we've seen) then the floor must also be higher off the ground.

[Lindz]

Anyone thought, that if the rear ride height is determining the rake, then the leading edge of the floor must also be higher than on the other cars?

To elaborate, if the roll hoop is higher (as in the comparison pictures we've seen) then the floor must also be higher off the ground.

From the comparison with the MP4-26 I would say that the leading edge of the tea tray is roughly the same height.

[horse]

Yeah I guess it might be possible to have the same height at the start of the tea tray, but then the start of the step plane (at the front of the side pods) must be higher. We've seen in the FEE thread that there is a lot of down force generated here.

It seems like Red Bull are laughing in the face of the preferred wisdom here that says ride height reduction is king.

[Lindz]

I just think that while most teams went a more conventional way of creating as much downforce as possible at the diffuser, Adrian Newey and his team have searched for efficiency and downforce everywhere BUT the diffuser. It's not nearly as important as it was with DDDs. By removing the diffuser out of the equation for a bit, I think they were able to find gains in many more places.

Then when they had the concept of the high-rake, low front wing, tricky bendy bits car, they designed a diffuser that would work in conjunction with that concept and claw back some efficiency lost from running it higher off the ground.

Many people say that the front wing not only produces downforce, it also 'grooms' the air for the rest of the car. It is the most important element of the new regs (especially with no DDD), and Newey+Co. have placed the RB7's design emphasis on it's efficiency (to apparent success so far).

[PlatinumZealot]

I just think that while most teams went a more conventional way of creating as much downforce as possible at the diffuser, Adrian Newey and his team have searched for efficiency and downforce everywhere BUT the diffuser. It's not nearly as important as it was with DDDs. By removing the diffuser out of the equation for a bit, I think they were able to find gains in many more places.

Then when they had the concept of the high-rake, low front wing, tricky bendy bits car, they designed a diffuser that would work in conjunction with that concept and claw back some efficiency lost from running it higher off the ground.

Many people say that the front wing not only produces downforce, it also 'grooms' the air for the rest of the car. It is the most important element of the new regs (especially with no DDD), and Newey+Co. have placed the RB7's design emphasis on it's efficiency (to apparent success so far).

All the diffuser does is allow the air to leave from under the car more easily. There is no suction at all. Think of the horn on a saxaphone. it is also a diffuser.

[Formula None]

1. Is it possible to increase/modify rake relative to speed? For example, simply have a weak 3rd spring at the front & a stiff one at the rear, to make the front end squat more than the rear.

2. Is it possible/legal to link the front & rear suspension in some way to achieve this?

3. Is there any way to make the rear end raise up rather than squat down as downforce increases?

[shelly]

I agree with bot6, marekk and lindz on rb7 being designed to work well around a different type of setting, with higher rake.
Also rb6 was.
I think taht a big part in this is played by composites.
If redbul has the kind of mastery in carbon fiber necessary to have a flexy wing compliant with the rules, it can as easily have flexibele:
-tea tray for aggressive rake
-side floor to increase rear downforce
-rear wing mountings to reduce drag
with the last two items compansating for high rake disadvantages.
So like Lindz says, it is more than flexi wing: it is a all-flexi car.

[Formula None]

Flexi Lexi?

[marekk]

All the diffuser does is allow the air to leave from under the car more easily. There is no suction at all. Think of the horn on a saxaphone. it is also a diffuser.

Sorry mate, but no.
All the diffuser does is to fill this empty space leaved behind it, as the car moves.
It uses air at inlet to achieve this - and because outlet area is bigger then inlet area, air have to go quicker at inlet.
It's really a pump, driven by car movement.