DDDs in 2010

[BreezyRacer]

http://twitpic.com/rv9fq



Seems that they are using some air coming in from above the floor to speed up the DDD exit air flow? Like one of those artist sprays where you blow across the supply tube to draw up ink from a bottle?

Interesting pic .. thanks! As for the triple decker it's likley that it has two inlets per side for totally separate ports to feed the additional levels of diffuser, so this is most likely arranged this way to facilitate a packaging delema.

Also interesting is how they "gave up" diffuser space on the sides to isolate the diffuser from tire turbulence. I am surprised that no one has done this before, during the season. I have been waiting to see it happen from someone. I'm a little surprised it was Renault though

[PNSD]

Breezy, RedBull, at least at the start of the season had their diffuser width the same width as the rear wing, that was when their endplates extended down as low as possible though. I think later on they increased the diffuser width.

[Mystery Steve]

See long post above...

See other long post above...

The split mass flow thing makes sense. I guess my assumption was that the control volume was large enough that "removing" from m2 and "adding" to m1 wouldn't be significant due to the total m being large enough to begin with. And yes, I definitely agree that you need additional energy to pull the air through, it won't do it by itself. This is where I see the lower rear wing coming into the picture. If designed with this in mind, you can have a pressure differential with a slightly higher pressure at the exit of the diffuser than at the underside of the wing, thus inducing a flow and "pulling more air" through the entire underbody. This is what I meant when I said the next best way to increase velocity (and pressure diffential across the floor) is to increase the mass flow.

My understanding is that the wing is the "second deck"... have I been off base the whole time? I'm feeling like I've missed something... And BTW, for anyone reading my posts on this subject, don't take me as the foremost expert even if my language makes me sound like I think I am. I am really trying to learn the diffuser design process myself for my F1000 car and my posts are more or less just me thinking out loud. So take it with a grain of salt .

[BreezyRacer]

Breezy, RedBull, at least at the start of the season had their diffuser width the same width as the rear wing, that was when their endplates extended down as low as possible though. I think later on they increased the diffuser width.

Yes, good point, RB did do that that and for a while they had a little VG panel extending out into the tire area there too. I was surprised that the went away from that and widened the diffuser to full width because in the past few years lots of efforts had been made to isolate the rear wheel turbulence from the diffusers. That's the reason everyone was building the rear deck right up to the rear tires as much as possible. I think it was Williams that had built too close for one race and cut their rear tires because they built too close. And the FIA passed rules to open up the wheel well area in an effort to take away DF. So isolating the diffuser seems quite important. It's good (for me anyways) to see someone playing around with that.

[ringo]

The renault third deck, is not really part of the diffuser; it looks like an augmenter to me. A thrust augmenter is something like a type of shield they put at the back of pulse jet engines to add mass flow to the exhaust. If it is cooler and denser it can create some kind of thrust.
(from aardvark.co.nz)
This is just a guess, since we are talking about a diffuser and not a jet engine.
Augmenters act like a "torque" booster (jet has no torque really) for the jet engine when operating at low speeds, since it's high velocity flow makes it very sensitive to the flight speed. Augmentor adds more mass flow at the exhaust and gives the engine better low speed characteristics and stability; since the PJ engine is driven by sound waves.

Maybe this third deck makes the diffuser very effective at slow speeds by adding air into the diffuser stream.

[PNSD]

Yes, good point, RB did do that that and for a while they had a little VG panel extending out into the tire area there too. I was surprised that the went away from that and widened the diffuser to full width because in the past few years lots of efforts had been made to isolate the rear wheel turbulence from the diffusers. That's the reason everyone was building the rear deck right up to the rear tires as much as possible. I think it was Williams that had built too close for one race and cut their rear tires because they built too close. And the FIA passed rules to open up the wheel well area in an effort to take away DF. So isolating the diffuser seems quite important. It's good (for me anyways) to see someone playing around with that.

After reading the regulations I was quite supprised that only RedBull turned up with the low-slung endplates, as well as the obvious increase in advertising space at first thought I expected a deeper endplate to increase rear wing efficiency and help mixing of the diffuser exit flow and rear wheel turbulence.

Perhaps you could shed light on the devices Brawn in particular have inboard of the rear wheels?

[BreezyRacer]

Yes, good point, RB did do that that and for a while they had a little VG panel extending out into the tire area there too. I was surprised that the went away from that and widened the diffuser to full width because in the past few years lots of efforts had been made to isolate the rear wheel turbulence from the diffusers. That's the reason everyone was building the rear deck right up to the rear tires as much as possible. I think it was Williams that had built too close for one race and cut their rear tires because they built too close. And the FIA passed rules to open up the wheel well area in an effort to take away DF. So isolating the diffuser seems quite important. It's good (for me anyways) to see someone playing around with that.

After reading the regulations I was quite supprised that only RedBull turned up with the low-slung endplates, as well as the obvious increase in advertising space at first thought I expected a deeper endplate to increase rear wing efficiency and help mixing of the diffuser exit flow and rear wheel turbulence.

Perhaps you could shed light on the devices Brawn in particular have inboard of the rear wheels?

I'm not totally sure which ones you're referring to but I'll take a guess .. the Brawn diffuser does indeed have a flatish floor to separate wheel turbulence from the diffuser but they block airflow exit to the back of the diffuser to create a low pressure area around the diffuser exit, thus theoretically increasing the low pressure in the diffuser itself. There have been many of these flanges/gurneys used this year. One of my favorite designs of these was introduced by McLaren where they added little tabs to the upper corners of the diffuser outside exits. I thought that was brilliant because it creates a strong low pressure area in the upper corner of the diffuser which reduces turbulence in the diffuser by encouraging diffuser flow to the outer corners of the diffuser exits. I'm not sure how effective it was, but RB did copy it for the last few races of the year. It's a nice little detail.

Brawn also have a lot of winglets emanating from the rear hubs towards the rear wing end plate area. Those are pretty straightforward, but Brawn really loaded up on them. Of course creating DF on the wheels is more effective because it doesn't have to pass it's loads thru the suspension, but technically this is a movable aero device that was allowed for Ferrari a couple of years ago and thus lives on.

[Richard]

By carefully engineering the vortices out the back of diffuser, you increase/maintain the velocity out the back of the diffuser where it would deaccellerate without the said vertices.
If the rules allowed for it (they don't), they would simply extend the diffuser beyond the back of the car and physically built sides and top to it. The vortices are kinda like a "virtual" extension of the diffuser.

Going off on a tangent....

Lets say you fitted a diffuser to a street car assuming there was suitable underfloor flow for the air supply. I guess the dirt on the boot/trunk would be different with and without the diffuser?

Sticking my neck out, I'm guessing that there would be less dirt on the number plate beacause the dirty air picked under the body is projected beyond the rear of the car by the diffuser?

[gambler]

would it be possible to get it working so efficiently that an
upcoming car could get a "slingshot" boost advantage? or
maybe "piggyback" some fuel mileage from the lead car?