Scuderia Ferrari SF71H

[CriXus]

With the talk about Ferrari's missing downforce at the rear, could you say from the image that Merc front wing creates more downforce? Kimi's wing has curve and looks much smaller.

Nice comparison.
Indeed it looks that Ferrari runs significantly less FW and at least the same amount if not more fo RW.
Looks alarming with regard to diffuser effectivity. A lot of work to do for the reds. Or to put it more positively: There is potential for significant gains.
I hope it's not due to their somewhat 'boxy'/steep coke bottle. Was a bit concerned when I first saw it. They had stagnation problem with a too boxy/steep coke bottle a couple years ago. Hopefully not a repeat.

Can you explain what is the problem with the shape? I am aero noob.

[Vanja #66]

https://www.racefans.net/wp-content/upl ... 606-13.jpg

With the talk about Ferrari's missing downforce at the rear, could you say from the image that Merc front wing creates more downforce? Kimi's wing has curve and looks much smaller.

That would be a no. We don't know the top view surface of these wings, we don't know the airfoils, we don't know the height of slots between flaps etc. Let's not even go to the outboard arch section On top of that, Ferrari seems to run front wing a bit closer to the ground (a bit more rake, but not as much as in Barcelona, as you said) and that can be worth a lot.

As for seemingly very low front wing AoA in mid section (between Y250 zone and arches), it's been there last year as well. It goes with side pod design, you don't want to have too much upwash from front wing to make those side pods work to their optimum. It's the same for Haas and Williams now (though Williams doesn't have Y250 zone as emphasized). Red Bull doesn't have top inlet, so they don't have to be as conservative with front wing.

I disagree. If you look at the tyre, Mercedes' wing covers the tyre almost up to the center, while Ferrari's is quite lower. I agree on the rear wing however, Ferrari's RW seems to have a larger frontal area than Mercedes. My guess is that their floor/diffuser isn't producing the expected downforce, so they run higher RW to compensate and lower FW to balance it out.

Can it have something to do with rake angle? Mercedes I believe runs the lowest rake angle of all teams, and I do believe that more rake pushes the center of pressure forward.

That rear wing is very telling. I didn't expect to see this at all. With Ferrari being better in speed traps while running so much rear wing shows the high aero efficiency design I wrote about after roll-out, they really reduced the drag wherever they could. Also shows PU isn't that far on peak power from Merc.

They went for longer wheelbase and new diffuser design. It's not surprising to read they have problems in the rear.

[henra]

Can you explain what is the problem with the shape? I am aero noob.

The problem is when the radius (seen from above) of the coke bottle in the undercut area is to tight, the adverse pressure gradient will become (critically) higher. When the adverse pressure gradient exceeds a certain value the flow becomes prone to separation (e.g. due to Yaw/slip or lateral wind gusts). If the flow separates, it will not follow the coke bottle shape any more, leading to an area with stagnating air. This in turn will block/reduce the flow to the upper side of the diffuser. This in turn leads to a higher adverse pressure gradient in the diffuser making it vulnerable for stalling itself. The problem is that in a race there are a lot of factors not present in the wind tunnel, so that in some cases the problem can't be reproduced in the wind tunnel. And it is often rather unpredictable.

[MtthsMlw]

They went for longer wheelbase and new diffuser design. It's not surprising to read they have problems in the rear.

Would you say that the lower cornering speed compared to Merc and Red Bull has more to do with the understanding of the car and the resulting set up work than with too low rear downforce which they have to fix with various updates of the bargeboards, diffuser etc.?

[Vanja #66]

Would you say that the lower cornering speed compared to Merc and Red Bull has more to do with the understanding of the car and the resulting set up work than with too low rear downforce which they have to fix with various updates of the bargeboards, diffuser etc.?

Well, reading those articles, it seems this car has loads of rear downforce in theory, with high rake set up. But, from whatever reason, it's not really working for them yet so they drop the rear end down a bit and loose some downforce there. This way, they loose front downforce from lifting the front wing up (due to lower rear ride height) as well. Some updates might solve this, or a bit different suspension set-up, we'll have to wait to see that.

[Mr.G]

Would you say that the lower cornering speed compared to Merc and Red Bull has more to do with the understanding of the car and the resulting set up work than with too low rear downforce which they have to fix with various updates of the bargeboards, diffuser etc.?

Well, reading those articles, it seems this car has loads of rear downforce in theory, with high rake set up. But, from whatever reason, it's not really working for them yet so they drop the rear end down a bit and loose some downforce there. This way, they loose front downforce from lifting the front wing up (due to lower rear ride height) as well. Some updates might solve this, or a bit different suspension set-up, we'll have to wait to see that.

Sounds promising to me. Little bit like Mercedes last year. They were struggling in the beginning too and then find the right set-up and was OK then.

[aral]

Could we please confine this thread to specific elements of the Ferrari SF71H. Comments about merits of rake , wing height etc are basically generic and should be in the aero forum.

[Vanja #66]

Fully agree with the conclusion, but to be certain you can increase the calculated area beyond the body of the mirror, lets say put the boundaries at the actual height of the mirror to the ground and 1m ahead and 1m behind the mirror.
I would like to see the result in that case. The larger volume would make a difference to the results. Also include an ordinary mirror for us to see what the real difference is with the best slotted one that you have designed.
I know it's a lot of work i am giving you but you already did quite a lot of work to get to this point.

ringo, here they are. I've used very long domain, 3m in total with 0.3m in front of mirrors. I had to reduce height and width of domain, to save some resources for finer mesh in slot area. Before doing that, I made sure the results and overall flow structures are near identical in this domain as in larger cross section domain.

Three types of mirrors were evaluated, SF71-H, SF70H and RB14. Results are interesting. But first, here are some dimensions and CAD model images.



Note that RB14's mirrors are smallest. They put the actual reflecting surface at around 20 degrees, reducing frontal area a lot. I've made sure the width of the actual mirror is 150mm.

Also, it should be said that RB14's mirrors were simulated in a manner corresponding to actual flow around them better than those of Ferrari. Ferrari's mirrors are also situated at slight angle, some 10 degrees is my estimate. However, I had to simplify this by putting them perpendicular to flow, to reduce the variables and see the difference between non-channeled mirror and current one.

Another thing is that flow coming around the mirrors is also diverted slightly outboard, because of driver's head and side crash protective structure around it. So all these simulations are accurate to some extent, but not 100%. Here are numbers for drag.



Unexpectedly, mirror design of Ferrari SF71-H turned out to produce most drag, by far. Part of the reason behind this is frontal area, which is 23% larger than that of RB14. Other part is larger frontal area exposed to high stagnation pressure. I believe that in reality both Ferrari mirror designs produce a bit less drag (still more than RB14), being at some 80 degrees relative to airflow, instead of simulated 90.

So, if not drag, what's the difference? Why did Ferrari do this? Let's look at turbulence intensity plots. Turbulence intensity tells us where the turbulence is strongest. More on this - here.


Turbulence plot - side view


Turbulence plot - top view

Again, no significant difference. Granted, turbulent core is fractionally smaller in SF71-H model, but nothing significant. 5% intensity is actually longest, mostly due to vortices forming on top surface. There is also a slight curve in turbulent wake, viewed from the side, due to longer top surface combined with channels. In my view, this shows us Ferrari adapted their design for overall flow in this area, where air begins do go down - pulled by low pressure on side pods. This is nowhere near enough for it to go into top inlet. Just writing this out for precaution.

Let us look at one more plot - total pressure plot. This tells us how much energy in air is lost because of turbulence. Aerodinamicists are always looking at getting as much high energy air as possible to the rear, to make sure both diffuser and rear wing are working the best they can. This is very important for overall flow of the car, since making diffuser work harder means speeding up the flow under the floor, reducing pressure upstream thus making the front wing work harder as well. This is why we don't have big wings in barge board area (only small ones guiding air down to the rear end, producing lift instead of downforce), even though teams are allowed to do it.


Total pressure plot - side view


Total pressure plot - top view

That's more like it, right? We see some clear differences in total energy loss between 3 designs, with RB14 and SF70-H showing very similar losses.

To conclude this, simulations performed suggest to us that Ferrari sacrificed some drag to improve air quality over the side pods (going further back and above diffuser) while also guiding it slightly down where it's wanted. If nothing else, this also shows us just how much team's value clean, high energy air - if all those vanes and wings in barge board area haven't been persuasive enough.

[MtthsMlw]

Great job Vanja!
I wonder if it is really necessary that the air goes through the mirrors or if you could achieve the same effect with a conventional closed design plus wings on the mirror housing without creating more drag.

[George-Jung]

So it is actually bending downwards on the current Ferrari SF71H....?

[ferkan]

Great stuff Vanja!

All that work, even on mirrors, just for floor/diffuser not to work.

Can you perhaps touch on the Henra's post from last page? I'm interested in your opinion komšija

I hope it's not due to their somewhat 'boxy'/steep coke bottle. Was a bit concerned when I first saw it. They had stagnation problem with a too boxy/steep coke bottle a couple years ago. Hopefully not a repeat.

[MtthsMlw]

Clear shot of the new diffuser even more simliar to Red Bull. Was only tested shortly in FP.



Still using crossed over S Duct.


AMuS

[Just_a_fan]

So it is actually bending downwards on the current Ferrari SF71H....?

Yes but not enough to get into the top rad opening. As stated by some of us previously, it appears to be aimed at improving airflow over the sidepods in lieu of the devices used by other teams.

[Sevach]

So it is actually bending downwards on the current Ferrari SF71H....?

Yes but not enough to get into the top rad opening. As stated by some of us previously, it appears to be aimed at improving airflow over the sidepods in lieu of the devices used by other teams.

Makes sense, with Ferrari's sidepod concept you end up without room to put those small vanes.

[Just_a_fan]

Makes sense, with Ferrari's sidepod concept you end up without room to put those small vanes.

Exactly. It was the obvious reason but some got fixated on a throw-away comment from a journo when the car was revealed.