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Old 12-31-2020, 02:17 PM   #11 (permalink)
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Originally Posted by JulianEdgar View Post
No one has mentioned OpenFOAM?

I know nothing about CFD (except that I see a huge amount of amateur stuff on the web that is obviously quite wrong eg in calculated Cd figures) but I know of an aerodynamicist using a professional(?) version of OpenFOAM.

Maybe I'm just dumb, but no one has quite explained how you develop the shape of your car to model in CFD - 3D scanning?

OpenFoam is here.
Usually you can buy a 3d model of your car, or find it for free on the various repositories.

Another way is to take a measurement to your car from a plane, say a garage ceiling, take a measurement every 5-10cm along the centreline, do the same thing 5cm to the left, and then again until the whole left side is complete. You then have multiple 2D slices of your car that you interpolate between to get the correct shape. Do it every few cm if the detail is more complex.

CFD doesn't need huge supercomputers contrary to what aerohead believes, I know people who run open-foam on middle range laptops. Open-foam is free. If anyone is using price or processing power as an excuse for not doing CFD then they are ignorant to the many ways of doing it.

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Old 12-31-2020, 03:48 PM   #12 (permalink)
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Usually you can buy a 3d model of generically similar to your car, or find it for free on the various repositories.

https://duckduckgo.com/?q=3d+capture...deos&ia=videos

3D capture is free on a smart phone. This generates a triangulated point cloud. The re-topo reduces the number of faces by orders of magnitude and reorders to quads. This reduces the task calculating the physics.
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Old 01-04-2021, 04:11 PM   #13 (permalink)
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Interesting article on CFD here.
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Old 01-04-2021, 04:52 PM   #14 (permalink)
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....I do not want to torture you with too many details. I’ll give you one example. [artificial viscosity]
The comments by Tomer (Tom) Avraham suggest the Navier-Stokes equations still need the insight that Steinmetz brought to Maxwell's equations.
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Open-source is typically closer to the measurement data
....we have done many benchmarks to compare codes each other or with measurements. The results completely confirm this. For example, in every turbomachinery benchmark, we have seen, open-source code gives a bit higher efficiency than commercial code. Open-source is typically closer to the measurement data.
This was also the conclusion of the national intelligence agencies. Open sources are more fruitful than covert sources.

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