In early March, Williams F1 intended to have an Augmented Reality (AR) unveiling for their 2021 F1 car, the FW43B, where fans would download an app on their phone that would allow them to view a 3D model of the car at the time of the unveiling. Unsurprisingly, the app was quickly unpacked by people on the internet, leaving us with the 3D assets for the car. This isn't an issue by itself, other models have been acquired for the 2019 Mercedes and 2021 AlphaTauri, however those were coarse models that have been simplified beyond use. The issue is that the Williams surfaces have a pretty decent resolution, even good enough for CFD. Shortly after the app was unpacked, the AR unveiling was called off, and the apps were pulled from all app stores. While many people have used the term "hacked", nothing was stolen from Williams servers. Williams released the app themselves, and people just knew how to extract the models.
You can find the model downloads in the original Reddit thread by u/Astorphobis.
I'm honestly a bit surprised that this wasn't foreseen by the people responsible for the app, but this incident shouldn't cause any competitive damage, so long as the rest of the paddock keeps it clean. Talking to a couple F1 Aerodynamicists, they received company emails addressing the matter, ranging from reminders that they can't be influenced by images from outside of FIA sanctioned events, to more strict instructions to not even look at them.
Thankfully I'm outside of those restrictions, but I can't assume the model is proper either, as there's a chance they used early/immature/wrong geometry in places. Further, there's parts of the car missing, and the parts that exist still have some issues with tesselation. These big caveats are why I'm referring to this geometry as the "FW43B(AR)", as I don't want it to make the hard claim that it is the FW43B. Given the above, the geometry isn't perfect, but it's certainly the best F1 model the public has ever gotten a hold of.
This is the first of three planned articles, and is entirely on the methodology I'm using to simulate this car. The purpose of this is to receive feedback on my methodology to work towards trustworthy results in later articles, as I'd like to treat this project with caution to avoid presenting anything misleading.
Since I'm not qualified to say where my CFD is right or wrong, I've consulted with a number of former F1 Aerodynamicists on the geometry, setup, and results, and have shared their feedback within the article. Since they're sharing more info than their former employers would likely prefer, they will be kept anonymous, and will be referred to as Aerodynamicist 1, 2, 3, etc.
CFD is a complex beast, especially when you combine it with complex aerodynamics such as those in Formula 1. So, before anybody gets wooed by my pretty pictures, I'd like to bring up a quote that originated in statistics, and is often used within the context of CFD:
Strictly speaking, my CFD is wrong, so it's just a matter of doing my due diligence to make it as not wrong as possible, and knowing where to place skepticism in my results. That being said, my setup is fairly similar to run-of-the-mill F1 CFD, so if it can be useful at the F1 level, it can be useful here.
Aerodynamicist 2: "This is absolutely spot on. CFD is wrong, and we knew it, we just strove to make sure it was still useful to us. With the new regulations, doing that will be more important than ever."
For this first article, I'll be keeping the model quite similar to the original geometry from the app, with only minor fixes to make the model behave in CFD, and a few replicable things like the driver model, wheel MRF volumes, and porous brake rotors. This is mainly to provide results that others can replicate and compare against their own attempts at simulating this geometry. For article 2, I'll be redrawing as much of the missing features, and implementing any feedback from this article. Finally, article 3 will present CFD results that will be our best shot at having "real" F1 CFD results.
The audience of this article will include a wide range of CFD knowledge, ranging from F1 Aerodynamicists to aero-interested F1 fans, so while I'm getting into the nitty-gritty, a bit of technical language is worded down for the public as necessary.
First, a rundown of the model, covering what is missing from the model relative to a full geometry, and issues with the models that had to be fixed to run CFD. Since the model only needed to be used for rendering, it's quite "dirty", requiring many hours of surface preparation to create a proper model. Shown below is my CFD software' (STAR-CCM+'s) surface repair tool, where red errors indicate faces that intersect each other, green lines indicate free edges that result from unclosed surfaces, and blue errors indicate non-manifold errors, where edges or vertices (points) are shared by multiple surfaces. All of these are critical errors that should be fixed to generate a proper mesh.
The foremost thing to note is that the geometry was uploaded to the app as a mesh body, meaning it has already been pre-tessellated from the spline driven CAD. As such, there's a limit on the curvature that can be resolved. Here's some 8K screenshots giving a rough idea on what we're working with, open in a new tab and zoom in:
This tessellation has a larger impact on smaller geometries, an example of which can be seen in some example pressure profiles for the front and rear wings, both using a 5mm surface sizing. This is caused by the tessellated surface having inconsistent curvature, where the flat faces of the tessellation will have a lower pressure due to less curvature, and the edges will have a higher pressure due to high curvature. This is much more significant for smaller features like the bargeboards and diffuser elements.
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