Zynerji wrote: β25 Jun 2021, 14:53
PlatinumZealot wrote: β25 Jun 2021, 03:47
Zynerji wrote: β24 Jun 2021, 13:23
Just going to copypasta the PM I sent JaF here since there's interest.
How does that tie into the CFD mesh?
Because the mesh nodes are what are culcated.
And as rays are straight lines how does that work say around a curve? Like the curves of the car?
Hard to see how that works for F1 CFD.
Two different techniques. Im not a programmer but I was a user of ray-tracing and CFD. So this is interesting but you have to explain this one.
It is point cloud, so no mesh. The conjecture was to use the rays to "erode" the point cloud and leave shapes behind that generate the desired flow-fields around the object.
The "bounce behavior" can be turbulent (curved) with added ray collision detection. The horsepower to calculate was the only issue. The bi-directional nature of the ray caster allowed you to pick where you want any ray to start and end. That was what gave this generative modeling concept power, as you could use the BiRT to bundle the rays by density, and generate a model to run in an actual CFD software to correlate.
He/we never explored much past that conversation, so I'm sure there are more devils in the details. It just seemed reasonable to speculate that someone has done this by now with the huge computing power available in a multi-GPU desktops and super-computers.
But the challenge with CFD as opposed to ray tracing is that fluid packages are continuously mutually interacting, while photons are not. It's not just bouncing off the surface - it's the continuous bouncing in the air itself that makes the problem much harder. At least, that would be my first impression. Please do correct me if you think otherwise.
Anyway, accounting for those fluid-fluid collisions in a rational way (not in a completely mesh-free environment, which is workable for rarified gases but seems a bit outlandish for dense ones), you effectively get to Lattice-Boltzmann simulations, where large numbers of mesoscale fluid particles are streamed between grid-nodes, and collision models account for the rest. And lo and behold, these type of simulations do work very well on GPUs, and are now quite competitive with finite volume (or substantially better) in several applications. But that's not really new and earth-shattering, it's a continuous development. I'm not sure how these simulations are leveraged by F1 teams though. Many seem to be partnering up with Siemens or ANSYS for the time being, and while ANSYS is working on introducing LB in Fluent, it's certainly not mature yet. And with LB being intrinsically dynamic, steady-state FV may still win on overall computation time, for the time being.