Diffuser functions

[shelly]

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.

Ther is suction in fact. The suction peak is on the diffuser kink line

[bot6]

I have a feeling my first article on the F1T wiki will be about how diffusers work.

More specifically on the RB7, what impresses me about this car is that it's a completely integrated package. The high back with augmented diffuser volume, the exhaust used as side fences making it more efficient, the slender, long shape, the flexible lowering front also using the rake... It just all works together, blends together...

It's kind of intellectually beautiful that way. And Flexi Lexi would be a nice name for it, better than kinky kylie.

But such an integrated package does make specific upgrades more tricky to pull off as you risk upsetting the balance.

Lindz, now I get what you mean. But by raising the rear, you raise the diffuser too, hence increasing the volume under it. So the diffuser / floor volume proportion won't change drastically. It's a linear increase by the same proportion for both (as geometrically they are still aligned, being "raised" at the same time) so the proportions should stay the same. Just a bit of a strange application of the Thales theorem.

[PNSD]

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.

Ther is suction in fact. The suction peak is on the diffuser kink line

Well, theres two suction peaks I believe. The first, and largest being the splitter, then there's a peak with at the diffuser throat, as you state.

[horse]

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.

To me, you have an interesting counter-play going on. If the car is an upside down wing, just to illustrate what I'm getting at, and the RB's rake is being set by the rear end of the car, then there is a trade off between changing the angle of attack and lowering the car. By increasing the rake, the wing's angle of attack will have increased but this will also raise the ride height slightly. Alternatively keep the rake less, and therefore angle of attack, but get a lower ride height.

I've not seen such a study on this before. I've read studies about increasing diffuser angle and, in that case, the onset of diffuser stall occurs at higher ride heights. However, the maximum downforce of increasing the diffuser angle is more than having a lower ride height and a smaller diffuser. It's hard to judge if changing the angle of attack of the whole car has a similar impact, however.

[Robbobnob]

After all this talk i cant wait to see the RB7 let loose on some of the better corners this year.

Thinking about the rake, and the mechanics that would affect it, would it be possible for them to be running a sort of Z-bar set up, to keep ride height with high downforce whilst leaving a relatively soft spring rate for cornering.

dont know a whole lot about f1 suspension mechanics, is a field i really want to study... when i dont have soo much uni

[PlatinumZealot]

Ther is suction in fact. The suction peak is on the diffuser kink line

Diffuser do not do work. Thermodynamics.

Suction is the opposite of pumping. which are both forms of work.
To suck something has to do work.

It only looks like the diffuser is suction but in reality the ORIGINAL stream of air front the front of the car is expanding at high speed. Diffuser is just facilitating it.

OK.. i know people say I like to bring up "unrelated stuff" but Air conditioning systems, and turbines use diffusers to make expansion to atmospheric more efficient. Less ducting losses.

Inside is lower than atmospheric, so it is easy to say it is sucking, (if you tap the diffuser throat air will be sucked in from outside.) But since suction is work what is doing the work? In fact doing this will cause the machine that is doing work to lose power. Your turbine will loose power and your AC system will experience more ducting loses, so the fans will need to do more work. So in these cases something is doing more work to make up for tapping the throat of the diffuser to get suction.

butRemember the diffuser itself is not doing anything. Take the formula 1 car, what is doing the work? The car. The car is "pushing" the fluid under the floor.
If you follow the original streamline of the fluid from beginning of the front splitter you will see that it is not being sucked, because the air is actually moving from low pressure from the throat of the front splitter, to a slightly higher pressure in the diffuser throat to higher pressure at the end of the diffuser. (expansion to atmospheric) Suction is not low pressure to high pressure is it? That is why you have to be very careful with this.

The trick of pointing the exhaust near the throat of the diffuser might make it seem that the diffuser is doing the sucking as well (like the tapping I mentioned before). And just like the tapping example I mentioned before something has to do the work to make the suction happen. The diffuser cannot do it, so what is left is the car or the exhaust gasses and the atmosphere. You know what this means? Your car will work harder when you tap the diffuser. It will be seen as more drag under the floor. Or if you wisely use the exhaust your exhaust will loose some of its energy, which is actually not bad at all, since it's not going to be used for anything else anyway.

That is just my take though. I always try to work from the fundamentals.

[marekk]

@n_smikle:
And where comes downforce from in your model of diffuser ?

[shelly]

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.

Ther is suction in fact. The suction peak is on the diffuser kink line

Well, theres two suction peaks I believe. The first, and largest being the splitter, then there's a peak with at the diffuser throat, as you state.

Agree with you, there are two. I think the diffuser one is bigger, that's why I quoted just it to fix a point.

[volarchico]

@n_smikle:
And where comes downforce from in your model of diffuser ?

Probably where all downforce comes from when you base it on physics: pressure distribution.

[Muulka]

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 to break you analogy, but the bell on brass instruments is there to increase the sound

OT: Just wondering, how did the DDD help produce downforce if a diffuser creates none? Did it simply let more ai pass more easily from the underside of the car?

Does the downforce that we would say that the diffuser helps to make be centered along the flat bottom?

Just trying to learn

[myurr]

OT: Just wondering, how did the DDD help produce downforce if a diffuser creates none? Did it simply let more ai pass more easily from the underside of the car?

Does the downforce that we would say that the diffuser helps to make be centered along the flat bottom?

Just trying to learn

That was my armchair understanding. Hence teams like Williams designing specific parts to feed more air underneath the front of the car (in their case the snow plough), and using the diffuser to draw that air through. This is also why the centre of pressure is under the car instead of being within the diffuser.

[hollowBallistix]

I thought the whole point of the diffuser (Diffuse - To spread over or through as in air, water, or other matter, especially by fluid motion or passive means.) is to efficiently allow the low pressure, fast moving air under the vehicle to rejoin the high pressure slower air more efficiently, doing so improves the flow under the vehicle, hence better downforce & little drag.

the whole DDD allowed for this air to be managed better, so creates less of a stalling point under the vehicle, so effectively the flow is much better and this is why you get better downforce, more flow = less pressure = more downforce & this is what their trying to replicate by blowing the exhaust gasses in this area this year.

[tok-tokkie]

Thanks for that explanation Smikle. I get a bit confused by the posts but when you revert to the basics it is relatively easy to distinguish between the wood & the trees, the accurate & the deluded posts. I had lost track of the basics.

[djos]

That (the situation, not problem) sounds eerily similar to what was said of Seb's problem right around the Monaco time

Wasnt that supposed to be carbon bonding failure somewhere deep in the chassis? (too much kerb bashing? )

[PlatinumZealot]

[...]