Venturi vs flat floor

[Hoffman900]

Exactly... And that’s why context matters. In aerospace, F1 car speeds are trivial, and below Mach 0.3, compressibility effects are so minor they’re not worth obsessing over. That’s not opinion, that’s standard engineering practice backed by physics.

Some people confuse the existence of compressibility with its relevance. That’s how you end up with arguments about air compressors in a conversation about underbody aerodynamics. It’s a classic case of knowing just enough to sound confident, but not enough to be correct.

Just for context... Some of us have already gone down this road with OP in earlier threads. The conversation tends to spiral into circular logic and cherry picked doubts, which is why I’ve learned it’s best not to overinvest there. Your post adds value though, and I hope it lands better than some of our previous attempts did.

Another poster here who use to do the same admited he got his ideas from “conversations” with ChatGPT. A lot of these actually wrong but psuedo smart posts / ideas, likely originate from that.

I’ve long since deleted reddit, but you’re seeing the same there in what were technical subs. People posting with questions / responses that are clearly “AI” generated and full of errors.

Yeah, I’ve seen that trend too... Especially in car threads. Sometimes discussions get flooded with confident sounding takes that don’t hold up when you look closer. It’s like people discovered buzzwords without understanding what any of them mean. Makes it harder to have real technical conversations, which is a shame because there’s a lot to learn when things stay focused and grounded. That’s why I usually stay out of it now. I see you got to experience OP for yourself.

F1 Tech Twitter, Sam Collins, and the F1 media sphere and wannabe influencers etc all don’t help with this. They’re often misinformed and wrong.

[Silent Storm]

Run a study my friends.
I did not say density dominates what happens under the car. None at all. I am saying it is not a negligible parameter.
This is exactly why at the Mexican GP, in less dense air, the cars behave differently around the track. Am I right or wrong? And there are many engineers on this forum; maybe not aerospace but dime a dozen. Chat GPT would probably give me nice long paragraphs make me look smarter; I should try it.
As to be specific about the floor under the car. It would be helpful with an actual study of a ground effect floor model.
Or if there were some guide from an insider as to what objectives drives the shape of the front, and middle prior to the diffuser.

You’re shifting goalposts again, Ringo... First it was about “density changes under the car” being fundamental to how flow behaves, now it’s suddenly “not negligible” and about Mexico’s altitude. Two entirely different discussions, and you’re trying to blur the line between them.

The Mexico example is macro environmental and affects the whole aero package like cooling, drag, downforce, not the localized flow behavior under the floor where Ma < 0.3 and compressibility is minimal. No one said density is irrelevant... We said it doesn’t dominate or fundamentally change how underfloor aero behaves in that regime. And that’s supported by actual CFD practice, not selective interpretation.

“Run a study” is rich coming from someone who’s made a habit of asking others for proof while providing none themselves. You’ve repeatedly shifted the goalposts and leaned on vague generalities instead of offering any real data or technical breakdowns. If you’re confident in your point, you should be the first one backing it up with specifics, not outsourcing the burden to everyone else.

I actually agree with you... Based on your recent posts, you might benefit from ChatGPT. At least your replies would stay consistent.

[Hoffman900]

Here is a paper published in the SAE Journal that ran (unvalidated) CFD on their best guess of the RB18’s geometry, and at various ride heights:
https://bpb-us-e1.wpmucdn.com/you.stony ... 602aa3.pdf

You can see how the strakes work as well as how the floor ingests air along its length. As seen / pointed out by Willem Toet as well.

[Silent Storm]

Here is a paper published in the SAE Journal that ran (unvalidated) CFD on their best guess of the RB18’s geometry, and at various ride heights:
https://bpb-us-e1.wpmucdn.com/you.stony ... 602aa3.pdf

You can see how the strakes work as well as how the floor ingests air along its length. As seen / pointed out by Willem Toet as well.

Thanks for sharing that... I’ve come across the paper before, and while it’s based on unvalidated CFD and estimated geometry, it’s still a solid attempt to explore broad trends. Definitely helpful to visualize how the strakes and floor might be working in principle.

Appreciate you bringing technical material into the mix, It’s refreshing when the discussion is grounded like this.

[Hoffman900]

https://www.mdpi.com/2227-7390/13/9/1455

Investigating the Impact of Structural Features on F1 Car Diffuser Performance Using Computational Fluid Dynamics (CFD)

Abstract

This study utilizes Computational Fluid Dynamics (CFD) to optimize the aerodynamic performance of a Formula 1 (F1) car diffuser, investigating the effects of vane placements, end-flap positions, and other structural modifications. Diffusers are critical in managing airflow, enhancing downforce, and reducing drag, directly influencing vehicle stability and speed. Despite ongoing advancements, the interaction between diffuser designs and turbulent flow dynamics requires further exploration. A Three-Dimensional k-Omega-SST RANS-based CFD methodology was developed to evaluate the aerodynamic performance of various diffuser configurations using Star CCM+. The findings reveal that adding lateral vane parallel to the divergence section improved high-intensity fluid flow distribution within the main channel, achieving 13.49% increment in downforce and 5.58% reduction in drag compared to the baseline simulation. However, incorporating an airfoil cross-section flap parallel to the divergence end significantly enhances the car’s performance, leading to a substantial improvement in downforce while relatively small increase in drag force. This underscores the critical importance of precise flap positioning for optimizing aerodynamic efficiency. Additionally, the influence of adding flaps underneath the divergence section was also analyzed to manipulate boundary layer separation to achieve improved performance by producing additional downforce. This research emphasizes the critical role of vortex management in preventing flow detachment and improving diffuser efficiency. The findings offer valuable insights for potential FIA F1 2023 undertray regulation changes, with implications for faster lap times and heightened competitiveness in motorsports.

Authors from the Alpine team and Oxford.