What exactly is the DDD advantage?

[raymondu999]

Hey all... just curious to know this. What exactly is the advantage of the DDD? Is it just that there is a larger surface area, meaning the inherently larger diffuser at the back? Or is it something more fundamental?

[TheMinister]

I was under the impression that the DDD was allowing the angle of the wing (or surface if you want to get picky, it's only the underside of a wing I suppose) to be greater, as having a second element underneath lets you throw the air up more without stalling.

It's simply about not creating too big a problem for the air to stick to the bottom of the diffuser.

Mangled explanation I know, was trying to think of some simple explanations to compare it to, but couldn't really think of any (biplanes maybe, multi-element front wings maybe, but none seem quite the same).

Edit- aha, just thought of a good example; remember the ferrari a few years back had a sort of extra 'winglet' tacked onto the centre bottom of it's rear wing? (sorry can't find pictures) Exactly the same as that; helps prevent stall at greater angle of attack.

[marcush.]

there is a certain slope of the difusser which is the maximum you can in terms of being steep before having separation.this of course is also a question of how much air you are getting under the car .if you are running low and don´t get much air under the car separation should be a bigger issue than if your cat can walk under the thing without having to watch her head..
as you have the low plank area which is covering almost one third of the bottom area
allows for a big difusser (length) but the side difussers -for the outer ,higher areas of the floor -are very short and less effective,there was a need to work the outer sections of the underfloor harder,pulling air from them by something different then those rudimentary side difussers.
The slots in the vertical steps in the underfloor feed a second deck expanding into
a big difusser obethe centre section of the normal difusser allowing to work the stepped up side floor sections harder .

that is how I understand it.

[BreezyRacer]

The sole advantage of the DD diffuser is that you can start the diffuser sooner, like any good engineer would like to. These cars would be faster if you didn't have to deal with DD diffusers by themselves, but since the rules are written the way they are a DD diffuser allows them to get a better diffuser setup by starting the diffuser earlier in the floor and higher out the back.

So it's simply a rules packaging deal. A plain diffuser would work better if the rules didn't restrict it's size and location.

[TheMinister]

there is a certain slope of the difusser which is the maximum you can in terms of being steep before having separation.this of course is also a question of how much air you are getting under the car .if you are running low and don´t get much air under the car separation should be a bigger issue than if your cat can walk under the thing without having to watch her head..
as you have the low plank area which is covering almost one third of the bottom area
allows for a big difusser (length) but the side difussers -for the outer ,higher areas of the floor -are very short and less effective,there was a need to work the outer sections of the underfloor harder,pulling air from them by something different then those rudimentary side difussers.
The slots in the vertical steps in the underfloor feed a second deck expanding into
a big difusser obethe centre section of the normal difusser allowing to work the stepped up side floor sections harder .

that is how I understand it.

We should team up, I do the spelling and you do the words. Exactly what I wanted to say, only better.

Suppose there's no restrictions at all on the diffuser design; what is the best thing to put? Any wing elements underneath the bottom surface of the diffuser? Would they extend backwards from the car?

[marcush.]

haha ...ok

[raymondu999]

So then. Would a double diffuser, in a certain shape and dimensions, be better/worse than a single diffuser of the same shape and dimensions?

[xpensive]

I believe the answer can be made a little simpler than the above. In order to reduce downforce for the 2009-season, it was decided to further limit the allowed cross-section area of the diffuser, looking from rear.

Most teams designed according to this, but some creative engineers at Honda found a loophole in the regs, where vertical "slots" in the diffuser together with the crash-structure opened up more area, which increased air-speed under the car, in turn increasing downforce.

[marcush.]

to me the whole thing is hinging on the thing that we have lateral steps in the floor and the higher outer sections should ,as a lot more air passes through them
combined with the short difussers give not much scope for producing downforce .
The slots open diffusser area that is simply not available in the current regs under conventional interpretation ,as there is only the length and height of the difussers as defined in the regs,so the draw from these rudiments is never enough to exploit the air that is fed along the high step floor area without the slot and DD