Scuderia Ferrari SF71H

[OO7]

If the air is expanding in the expected fashion, wouldn't this reduce pressure over the diffuser rather than increase it.

Does the pressure in diffuser decrease or increase when air starts to expand?

https://ibb.co/bGF1OS

It begins to increase, however the pressure is still significantly less than freestream.

[Vanja #66]

Of course it is, you'd need a lot bigger and longer diffuser to expand it to Cp=0 without separation.

[TwanV]

How do you mean Vanja? A diffuser by definition is a compression device to allow the accelerated flow under the car to decelerate to free stream(the car's) velocity. From my (very limited) understanding of f1-diffuser aerodynamics, the downforce comes from: 1.) accelerated flow just upstream the diffuser (pressure drop due to venturi effect ->suction to the road) and 2) the diffuser itself directing the flow upwards, thereby pushing the diffuser down.

(Not sure if 1) is allowed as a venturi perse due to floor regulations)
Or is there more to it?

[Maritimer]

Pretty sure the entire diffuser experiences lower pressure, not just the area ahead of it. The more volume you have a given mass of air trying to fill, the lower the pressure must be. The drop is greatest where velocity is highest, but there should be lower than ambient pressure across it's entire lower surface.

[OO7]

Pretty sure the entire diffuser experiences lower pressure, not just the area ahead of it. The more volume you have a given mass of air trying to fill, the lower the pressure must be. The drop is greatest where velocity is highest, but there should be lower than ambient pressure across it's entire lower surface.

Exactly, this is why the Ferrari device is confusing. If it functions similarly to a venturi tunnel, the airflow around the exit will be of a higher pressure than around the throat, however it will still be of a lower pressure (I'd think) than the air flowing around its outside.

[Maritimer]

Pretty sure the entire diffuser experiences lower pressure, not just the area ahead of it. The more volume you have a given mass of air trying to fill, the lower the pressure must be. The drop is greatest where velocity is highest, but there should be lower than ambient pressure across it's entire lower surface.

Exactly, this is why the Ferrari device is confusing. If it functions similarly to a venturi tunnel, the airflow around the exit will be of a higher pressure than around the throat, however it will still be of a lower pressure (I'd think) than the air flowing around its outside.

Would that not have a scavenging effect on the primary diffuser? Since the pressure over the tunnel would be even greater than flow over the diffuser with nothing in the way. The air that has to move around it would make a low pressure pocket above the center of the diffuser, like a gurney flap on steroids.

Could it be used to extract hot air from the engine bay? As a way to induce suction at the inlet and "gain" airflow across the rads? Like a passive fan but one that works better the faster you go.

I can't tell if they're attached to the main bodywork or not so correct me if I'm way off here.

[Vanja #66]

You can't look at it as a simple diffuser. There's a wall of flaps and the actual diffuser in front of it, increasing the pressure in the first place.



Look how struts (for trailing edge flaps) alongside it are placed - pretty much at the same angle like the tunnel walls at the contact with the top of diffuser. This is telling you how the airflow behaves in this area even without flow viz. It's the same for any strut on the car, it's placed in the direction of airflow to be the minimal obstruction. Though, sometimes, they could be used as vortex generator as well, I imagine.

[Benard Bonhomme]

If the air is expanding in the expected fashion, wouldn't this reduce pressure over the diffuser rather than increase it.

Does the pressure in diffuser decrease or increase when air starts to expand?

https://ibb.co/bGF1OS

If you cut the diffuser in a y plane, you are in this configuration :

- under the floor, the air is travelling at the velocity v1, pressure p1 and the distance between the track and the car floor is d1
- at the exit of the diffuser, its velocity is v2, pressure p2, and the distance between the track and the car diffuser is d2

If you suppose that you live in a perfect world, the flow rate is conservative (it is more or less true in real conditions, but it's close to reality)
So d1*v1 = d2*v2 (Venturi effect)
This means that v1 > v2

In a perfect world again, the Bernouilli equation says that:
1/2*rho1*v1^2 + p1 = 1/2*rho2*v2^2 + p2

If we assume we are in a straight line at constant speed on a perfect track: rho1 = rho2

This means that p1 < p2

There are a lot of assumptions (perfect world = no viscosity) while the Reynolds number is not that high. But the general idea is here

[TwanV]

I'm at work sadly but hope this might help in discussions http://www.racetechmag.com/2017/08/will ... diffusers/ ; still trying to get my head around what actually happens in a modern F1 diffuser.. and I have a degree in aerodynamics .

[Morteza]

Via AMuS

[Kalsi]

Not sure if this is really a problem like the tweet says... but it seems to be happened near the last race simulation Seb just did.
The giant smoke cloud is only to be seen on engine start, and it does not look like it has anything to do with the "oil breather"

https://twitter.com/Berrageiz/status/97 ... 92/video/1

[MtthsMlw]

Not sure if this is really a problem like the tweet says... but it seems to be happened near the last race simulation Seb just did.
The giant smoke cloud is only to be seen on engine start, and it does not look like it has anything to do with the "oil breather"

https://twitter.com/Berrageiz/status/97 ... 92/video/1

Indeed it does not look like the smoke is coming out of the crash structure

[Vanja #66]

I'm at work sadly but hope this might help in discussions http://www.racetechmag.com/2017/08/will ... diffusers/ ; still trying to get my head around what actually happens in a modern F1 diffuser.. and I have a degree in aerodynamics .

In today's diffusers happens everything as Mr Toet written, of course (this freak read that article at least 6-7 times before, btw ). But much more as well, you have additional vortex generators, flaps around trailing edge, turning vanes, every little piece of carbon fiber allowed by rules to help with aggressive flow expansion without separation (where it's unwanted).

As for double deck diffusers, this article of Mr Toet is pure gold:

https://www.linkedin.com/pulse/mysterie ... llem-toet/

As you can see, this tunnel would be nothing of the sort, but have no doubt it improves overall performance.

[LM10]

In the first couple of days of the first week of testing Ferrari seemed to be planted quite well. It was told that them and RBR looked better than Mercedes which were a bit wiggly yet. However, towards the end of first week it kinda was the other way round between Mercedes and Ferrari.

Mercedes getting better with more laps and optimizing setup seems just to be a logical consequence of testing time. But how to interpret the decreasing stability of Ferrari? What could be the reason behind that?

Comment by Ferrari president on new car:

"As for Ferrari's chances of winning the title in 2018, Marchionne said he is feeling "relaxed". "It's definitely the quietest season I've faced since arriving in 2014," he revealed. "The boys are in control more than before. We have all the conditions we need and I think the car can be a winner at 51 per cent of the races this season."

Thank you for answering my question indirectly.

[dankane24]

https://twitter.com/ScarbsTech/status/9 ... 17248?s=19
Scarbs has a good drawing of the diffuser.