Vanja #66 wrote: ↑Sat Feb 19, 2022 10:03 pmHello everyone, as promised - here's some CFD work. Big thanks to jjn9128 for providing the base 2022 car model, as well as Vyssion for support and advice.
To examine the concept of F1-75, a base model was reworked and F1-75-like sidepods were added - let's call them tub-sidepods. Please note, the rest of the model is fairly generic and nothing except the rough idea of how F1-75 sidepods might work should be taken away from these results.
To begin with, let's examin iso and top views. The third picture is from a model without the tub, just a "flat" surface, almost like Aston Martin.
https://i.ibb.co/2ynvgv5/comp-iso.jpg
https://i.ibb.co/qd9mn28/comp-top.jpg
https://i.ibb.co/HF4K05j/comp-noindent-top.jpg
It's clear right away we have several areas of interest - intake, upper surface and rear surface.
The area under the tub-sidepods intake is a high pressure zone, working towards downforce on top of the floor and lift under the intake. No point in trying to figure out how much it helps and hurts overall, unless we had F1-75 geometry and Ferrari CFD setup.
The upper surface is fairly long, probably as long as it can be. On the front, we have some lift generated, as is the usual with the sidepods. In the rear, the tub, we have a higher pressure "pool" which is definitely helpful and one of the benefits Ferrari are looking towards, no doubt. Comparing the results, the overall effect on tub-sidepod comapred to base model is around 100% more lift (only on the sidepod). This is somewhat negated by downforce generated at the front of the floor, as mentioned. The difference is far bigger compared to "aston" sidepods, they are almost completely generating lift all over the top surface.
The rear surface of tub-sidepods works together with diffuser ramp upper surface to form an area of higher pressure. This adds rear downforce directly on the floor, but also increases the pressure on the rear of the tub-sidepod -reducing the drag. Compared to base model, tub-sidepod alone had 50% less drag. This looks a lot like the main reason Ferrari extended the sidepods all the way to the rear - to use this effect and reduce drag. So - F1-75 sidepods are not draggy!
As far as the gills go, they are very likely oriented so they follow the airflow, take a look at flow-viz of simulation. It took 3-4 iterrations to prevent the top leading edge from separating, must be the same for Ferrari and the reason why they raised the intake so much.
https://i.ibb.co/ZgPpS4S/comp-iso-detail.jpg
I'd like to point out again that the model is very rough and even the sidepod is very far from acutal F1-75.
I wanted to take a look at velocity plots, across the horizontal cross sections. First picture is 0.1m from the ground and the second is 0.3m from the ground.
https://i.ibb.co/2YQbNnC/comp-vplot-0-1m.jpg
https://i.ibb.co/smCNgr4/comp-vplot-0-3m.jpg
At 0.1m there is no clear benefit of front tyre wake outwash, as that's still at the floor height. At 0.3m the difference is clear, as well as the difference in airflow towards the rear tyre. At tub-sidepods model, the barge-board-like geometry created a wake going towards rear tyre, and the difference in pressure can also be seen at the first comparison picture. The low-energy wake hits the tyre and pressure-increase is a lot lower. Overall, and take this with a grain of salt, rear tyre drag decreased by more than 10% compared to base model.
In total, compared to base model the tub-sidepod model had around 1-2% more downforce which shouldn't be taken into account as this depends heavily on overall geometry and how all the parts are working together. What's really interesting is the drag benefit - tub-sidepod model had around 11% less drag than base model! According to jjn, the base model isn't too good to compare to in this matter, however I think this difference is significant and should be noted.
Since Ferrari had to extend the sidepods to use the ramp pressure increase to reduce drag, it looks like they made the tub to offset the lift this generates. This is very clear when compared to aston-like sidepods. Afterwards, Ferrari surely used all effects combined with cooling channel design and gills.
Hi, thanks! I'll try to make another sidepod design like Mercedes did during next week and test it out. No promises, but I will try.Emag wrote: ↑Sat Feb 19, 2022 10:40 pmThat's a great read, thank you for your time!
Though, as far as I understood, those numbers are all compared against the base 2022 car model.
Would love to see it compared against one of the slimmer concepts (particularly interested in Mercedes'), as that would be a far more interesting comparison in my opinion.
Nevertheless, thanks for clearing some misconceptions! Eye aero gurus who were calling the Ferrari fat and draggy will probably be a little more silent now
50 m/s, 180 km/h.JordanMugen wrote: ↑Sat Feb 19, 2022 11:04 pmGreat job Vanja #66!
This may be a silly question, but may I ask what flow speed/Reynolds number this is based on? 150, 180, 200 km/hr?
Thanks! Yeah, the entire car is the final 11% drag reduction I stated. Again, this is just a simulation of their idea and no numbers should be taken too seriously into account, but we can now safely assume they made this design for several reasons. The air to beam wing is actually going down, even though these sidepods have a flick. Rear wing has strong low pressure under it and the air is bent quite strongly as long as there is some room between rear bodywork and rear wing - like there always is.PlatinumZealot wrote: ↑Sat Feb 19, 2022 11:26 pmThanks Vanja. Great work as always.
Was your drag measurement for the entire car?
How is the air going to the beam wing?
I find this great.
Sorry, it's not, according to the author of the original CAD model.
Yes, the inlet is smaller as I wanted to mimick the F1-75 design. I'm not sure how accurate it was, but there is also strong stagnation-like zone between the inlet underside and the floor (visible on iso view). This zone mostly compensates the difference in inlet size of the models and is likely not present on the real car. I was too eager to see the results, so I rushed the modelling a bit and ended up with a problematic model.cooken wrote: ↑Sun Feb 20, 2022 2:18 amFirst off, chapeau and thank you for the incredible (and quick) work on this. Very cool!
I do have one concern though: When I look at the first two pictures, the sidepod inlet looks quite a bit smaller on the tub version. Was there any consideration given to ensuring equal inlet flow (shared across sidepods and roll hoop) between the two models? Is it possible that the tub version had favorable drag because it is ingesting less air?
I also wonder about the longitudinal positioning of the inlets between the two models, with the tub seeming further forward. It would be interesting to compare the traditional versus tub with the same positioning since less variable involved, but that's less of an issue really since we still get a valuable concept level comparison. I do note that this was done to some extent with the "Aston" version but most comparisons related back to the base model.
P.S. - Sorry if these are dumb questions, I'm a structural analyst and rarely go beyond mechanics/dynamics so fluids is a bit foreign.
Thanks, like I said before, I'll try doing that as well, I hope I will find the time.JPBD1990 wrote: ↑Sun Feb 20, 2022 3:34 amThis is completely incredible to me and so appreciated! I can’t imagine the time and effort that went into this. Thank you!
Given that I feel guilty asking but am so interested to understand further, is there any chance of also modelling the Mercedes’ for a ‘real world’ head to head comparison? As I’ve posted elsewhere, given recent history one has to assume Mercedes’ concept is valid, so it would be very interesting to have a comparison against a ‘yard stick’ like Mercedes’.
Thanks again!
No right now, but I can make them.
It is a joke!!
Outside of Mercedes and Red Bull, I don’t think the other teams had the resources to go this far with the concept.Froggolo wrote: ↑Sun Feb 20, 2022 7:07 pmif this solution is so beneficial and possible to be used or at least tried by other teams,
i would have hidden it as long as i could, but us italians like to show off
Vanja, thank you so much for your incredible work and the informations you bring to us mortals