"Constraint Body Heat Source" implemented yet?

About the development of the FEM module/workbench.

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stair
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Re: "Constraint Body Heat Source" implemented yet?

Post by stair »

Hi Bernd, HoWil

Thanks for looking at this.

I happen to prefer Elmer but I would assume that similar issues arise in generating a Calculix input file.

Ultimately I think that domain selection is essential, my typical use would have multiple sources with differing magnitudes. Unfortunately I do not have the skills to help with coding but at least knowing the constraint does not function at present means I know that I need to work round it.

May I suggest that the constraint is greyed out in the menu until someone is able to get it working

Stair
emaille
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Joined: Fri Aug 12, 2022 10:09 am

Re: "Constraint Body Heat Source" implemented yet?

Post by emaille »

Hey at all of you who are still here after four years,

First of all thanks for further developing FreeCAD and adding new functionalities during this long period of time.
Although about four years have elapsed since the last post, I think that I'm still struggling with a quite similar problem.
I currently try to simulate a transformer and as you probably know it has core losses. That's why I wanted to add something like a "volume heat generation". Please correct me if I'm wrong, but I think the ConstraintBodyHeatSource is the thing I need.

For testing purposes, I created a simple Box (Part) and added an Analysis Container, then a Material, ...
At the bottom I created a constraint temperature and now I want to add a Constraint Body Heat Source.

Before further explaining my problem, I want to ask one question: Is this feature still not working?
After answering this, there may be no reason to read the following lines : ).

I know that the unit of "Heat Source" is W/kg, but I didn't find any information on the entries that are required under "Constraint". What should I enter as "Reference", because when creating and simulating more complex models, I want to implement different cores with different heat generations and therefore it would be helpful to exactly locate the heat generation. I'm quite sure this is somehow possible, but even after searching on the internet for several hours, don't know. (Maybe I should update the wiki-article with the information you are hopefully able to provide)


Please don't hesitate to blast me if this question is extremely dumb (it wouldn't surprise me as I am quite new in FreeCAD). I this is the case, I want to apologize. Otherwise, I would highly appreciate any helpful answer or adwise!

Greetings
Emilia


Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.2
Locale: German/Germany (de_DE)
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NewJoker
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Re: "Constraint Body Heat Source" implemented yet?

Post by NewJoker »

emaille wrote: Fri Aug 12, 2022 11:02 am Is this feature still not working?
First of all, I definitely recommend using the newest available version of FreeCAD (0.21 dev currently). The FEM module receives lots of bug fixes pretty much all the time. In 0.21 you will notice that there's no References property for this constraint.

Unfortunately, it seems that if it works at all, it works only with Elmer. Nothing is added to CalculiX's input file.

This constraint definitely requires some polish - making it work with CalculiX, adding possibility to select region, implementing task dialog and maybe changing units (W/kg are not very intuitive). Hopefully, it will be done in the near future.
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uwestoehr
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

@emaille , to use this feature properly, you must use FreeCAD 0.20.1:
https://github.com/FreeCAD/FreeCAD/releases/tag/0.20.1

and on top of this patch collection: https://forum.freecadweb.org/viewtopic.php?f=18&t=71058

The body heat constraint is a special one for the Elmer solver. Currently it can only be used if the Analysis has only one body. The constraint is automatically applied to this body. Its unit is W/kg, so you need to calculate the weight of the body. However, at the moment we cannot guarantee that the solver output is sensible because even in Elmer's official tutorial the results are suspected.

Therefore I recommend to use either the heat flux constraint of the temperature constraint and there the "concentrated heat flux".
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uwestoehr
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

For the next major FreeCAD release the Body Heat Source constraint is properly fixed:
- one can apply several heat sources to several bodies
- there is now a task panel to select the body and enter the value (expressions for the value are also possible)

This fix cannot be backported for FreeCAD 0.20.x. If you need the fix, checkout the next weekly build: https://github.com/FreeCAD/FreeCAD-Bund ... kly-builds
Jee-Bee
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Re: "Constraint Body Heat Source" implemented yet?

Post by Jee-Bee »

Only in Elmer or also in Calculix?
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uwestoehr
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

Jee-Bee wrote: Mon Aug 15, 2022 7:28 am Only in Elmer or also in Calculix?
The Body Heat Source is Elmer-only. Calculix does not use this kind of heat input as far as I know.
emaille
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Re: "Constraint Body Heat Source" implemented yet?

Post by emaille »

Hey,

Thanks a lot for the quick answers with so many helpful information and I'm happy to see how this amazing project gets better with every new version.

I just clicked the download-button on freecadweb.org like an absolute greenhorn :roll:
You are absolutely right, the latest version is the basis to get all features, my bad.


I hope all of you will have a stress-free week!

Emilia
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uwestoehr
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

emaille wrote: Mon Aug 15, 2022 8:27 am I just clicked the download-button on freecadweb.org like an absolute greenhorn :roll:
You did everything correctly. FreeCAD 0.20.1 is not yet on the website because we don't have Linux and MacOS builds yet.
But Windows is available:
https://github.com/FreeCAD/FreeCAD/releases/tag/0.20.1
Jee-Bee
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Re: "Constraint Body Heat Source" implemented yet?

Post by Jee-Bee »

uwestoehr wrote: Mon Aug 15, 2022 8:10 am The Body Heat Source is Elmer-only. Calculix does not use this kind of heat input as far as I know.
I try to check this tonight or later this week. I think it is a pity that where Calculix is kinf of the default solver it is behind other solvers at the moment :(
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