/sci/ - Science & Math » Thread #12772683

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OpenFOAM solver equations

Anonymous Mon 01 Mar 20:02:08 2021 No.12772683 View Reply Original Report

Quoted By: >>12773856 >>12775055 >>12775103

i was looking at the equation the OpenFOAM solver uses to calculate forces and was wondering why the units dont check out? the equations im talking about can be found on: https://www.openfoam.com/documentation/guides/latest/doc/guide-fos-forces-forces.html

Anonymous

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Anonymous Tue 02 Mar 2021 01:23:00 No.12773824 Report

Quoted By:

I never really learned how CFD equations work under the hood. I just click the button and watch convergence go brr.

Anonymous

Anonymous Tue 02 Mar 2021 01:34:08 No.12773856 Report

Quoted By: >>12775040

>>12772683
idk about openfoam, but for many equations if you treat it as 2D or 1D, you lose a m or m^2

Anonymous

Anonymous Tue 02 Mar 2021 09:57:11 No.12775040 Report

Quoted By:

>>12773856
probably this
your surface area vector [m^2] becomes a surface line vector [m]. to get the force for your 3d situation you multiply with the real width

Anonymous

Anonymous Tue 02 Mar 2021 10:03:15 No.12775055 Report

Quoted By:

>>12772683
Did you use the correct units in your controlDict/whereever you specify the units?

Anonymous

Anonymous Tue 02 Mar 2021 10:25:33 No.12775103 Report

Quoted By: >>12775122

>>12772683
https://www.openfoam.com/documentation/guides/latest/doc/guide-applications-solvers-variable-transform-kinematic-pressure.html
there seems to be some normalization happening, maybe thats the reason. its odd that they use the same letter for both pressures despite them having different units though

Anonymous

Anonymous Tue 02 Mar 2021 10:34:41 No.12775122 Report

Quoted By:

>>12775103
Yeah, the solvers can make you go "who the fuck thought that was a good idea" quite often

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