Mercedes AMG F1 W04

[astracrazy]

sorry to go off the current subject being discussed but i just need someone to answer a question for me



on the front wing, i've read that in the inside cascade (syrtium - i think it says - logo) creates a vortex. Where is this vortex aimed? to go under the floor or around the bottom of the sidepod or somewhere else? whats its purpose?

the reason i ask is because i'm looking into my front wing design for the KVRChallenge

Thanks for your help in advance!

[SectorOne]

I´m not sure but i think the tip of it creates the vortex and if you draw a straight line back it seems to be aimed at between the bargeboard and cockpit.
i can´t say for sure though.

[turbof1]

It's for creating a vortex along the y250 axis. Importantly they want the airflow at the centerline of the car closed off from the disturbed airflow outside.

[scarbs]

The Sauber CFD video gives us a good idea...

[turbof1]

Yup, seems to confirm with what I said. Imagine all those vortices inboard of the front tyres interfering with the airflow underneath the nose. The diffuser would be gasping for air like a fish spartling on the dry. The vortices created along the y250 axis stop from intruding the area.

Mind you the r winglet isn't the only vortex generator along that line. There are a whole series of them along there, and each team has their own solutions.

[astracrazy]

ok thanks guys, so its really for the diffuser? It seperates the clean air under the nose from the dirty air around the wheels?

[turbof1]

There are some other benefits like redirectin the outward air. Each teams fills in their own details; the r winglet is also used to create a bit of downforce, but the vortex generator itself is mainly to seal the centre line from disturbing airflow. Disturbed airflow beneath the nose could also create a high pressure zone there, causing lift.

Just to explain it rudimentary: teams want a to create a (venturi) tunnel underneath the car, accelerating airflow underneath, lowering the pressure there and creating more downforce. As they are bodywork-restricted, they instead try to use vortices all along the car. It's really a system of them, like you can see on the Sauber car: the y250 axis vortice generators on the front wing are in line with the "turning vanes pylons" underneath the nose, which in turn are in line with the turning vanes underneath the nose, which redirect air coming from outside the centre, together with the barge boards, away from the centre, to the inside of the vertical turning vanes next to the sidepods. On the floor around the sidepods (not visible on the cfd), they have rised sections in the floor, which both create vortices along the edge of the floor, again to try to seal the floor off from unwanting higher pressure/disturbed airflow, and keep airflow around the sidepods closed in (also not visible on the cfd).

Just to show those 2 vortex generators on the r winglet are just a piece in the puzzle. It's a synergy of vortices and bodywork all over the place.

[godlameroso]

Just to add to Turbo's point keeping airflow separated is crucial for a stable aero map during yaw conditions.

[Huntresa]

The Sauber CFD video gives us a good idea...

https://pbs.twimg.com/media/BKiXUmkCAAAl5tL.png:large

But does sauber even run R-winglet ? Eventho the theory is correct for the vortex were speaking of, but that img, is that running R-Winglet or are they doing the same thing in another way, cause we do see the barge boards doing their job seeing the thick air coming off the underside.

[turbof1]

No, they aren't. However, the main principle is still the same; Sauber just uses different methods.



In respect for the Mercedes thread, I will not elaborate on the sauber car, but combine it with the cfd image and you should be able to see how they try to do it.

[bar555]

It's for creating a vortex along the y250 axis. Importantly they want the airflow at the centerline of the car closed off from the disturbed airflow outside.

The real headache is to create the described effect not in a straight line but when cornering . That's why teams experement a lot with such vortex creators or even choose not to use them at all .

[turbof1]

It's for creating a vortex along the y250 axis. Importantly they want the airflow at the centerline of the car closed off from the disturbed airflow outside.

The real headache is to create the described effect not in a straight line but when cornering . That's why teams experement a lot with such vortex creators or even choose not to use them at all .

Yes indeed! Like godlameroso said, they also want this in yaw. However, if not careful, the vortices will change direction and do exactly what they are designed to eliminate: messing up the airflow underneath. Large flat surfaces are helpful in that regard, straightening the airflow before it reaches the vortex generating tip. Hence the current trend of running oversized pylons. However, you can't do that everywhere, and it is really hard to design a system that works in every condition, straight or in yaw. Even if you get it right in cfd, it might end up being a mess on the track.

Explaining it is by far the easiest part .

there were times when teams didn't had to break their heads about it. Just wrapping it up in typical bodywork like oversized bargeboards was more then enough:


The day those were banned, all the engineers together cursed the FIA to oblivion.

[henra]

It would seem easier to achieve a better, more stable effect by getting more underneath the car from the sides, rather than trying to add in a new way of sealing what is already there, wouldn't it?

More stable yes, but you loose expansion ratio.
And expansion ratio equals downforce if the geometrical size of the diffuser is limited by regulation.

Maybe a slight excusrion into the basic theory behind:
A diffuser generates downforce due to Bernoulli's Principle.
That says that dynamic pressure plus geodetical pressure plus static pressure is constant.
So by accelerating air (increasing dynamic pressure) you can reduce static pressure. That is what a diffuser does.
In an ideal world the exit speed of the diffuser would be equal to free air stream speed.
Then the static pressure will decrease by the square of the Ratio of the area at the exit divided by the area at the throat.
Blowing air in from the sides (behind the throat) will reduce volume flow through the throat and thus speed (and thereby decrease of static pressure = downforce) assuming that Exit Speed remains free stream speed and geometry remains untouched. Basically you want as much Speed through the throat as possible.
You could try to press air underneath from the front however you need to make sure you don't get so much increased static pressure under the nose in front of the floor overcompensating this gain. You can trade front with rear downforce to some extent with this method, though.

[timbo]

So by accelerating air (increasing dynamic pressure) you can reduce static pressure. That is what a diffuser does.

Except that diffuser slows flow down

[variante]

Except that diffuser slows flow down

The job a diffuser has to do is to accelerate air at its throat: this is where downforce is created. Then (and only then), because of its geometry, it inevitably slows the flow down.