"Constraint Body Heat Source" implemented yet?

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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 9:12 am 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 :(
Indeed, CCX allows much more than we support. it provides also flow and electro simulations -> would be a good summer of code project for next year. @bernd , what do you think?
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Re: "Constraint Body Heat Source" implemented yet?

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@uwestoehr Do you know if it would be difficult to make this constraint work with CalculiX as well ? CalculiX's syntax for a body heat source is very simple:

Code: Select all

*Dflux
elset_name, BF, magnitude
where magnitude is in W/m^2 when standard SI units are used (or mW/mm^2 when mm are used for length).

Apart from that, maybe it would be a good idea to add a warning when a constraint not supported by the currently selected solver is used in the analysis. I know that this is usually explained in the documentation but it can be very misleading when someone submits an analysis, there's no warning and the constraint just doesn't work (while others do). It can lead to many errors.
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Re: "Constraint Body Heat Source" implemented yet?

Post by Jee-Bee »

NewJoker wrote: Mon Aug 15, 2022 5:32 pm ...
Thanks
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uwestoehr
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

NewJoker wrote: Mon Aug 15, 2022 5:32 pm @uwestoehr Do you know if it would be difficult to make this constraint work with CalculiX as well
...
where magnitude is in W/m^2
This is already available. We have the Heatflux constraint for this.

Note that W/m² is the flux through a face. The body heat constraint is in W/kg so really for a body, not a face.

I don't agree that we need special handling for constraints that are not available for all solvers. We have meanwhile proper Wiki pages describing the constraints. FEM requires some reading how it works. This way you will see that the flow constraints don't have an effect with CCX, the same with Electrostatic constraint, initial pressure...
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Re: "Constraint Body Heat Source" implemented yet?

Post by NewJoker »

uwestoehr wrote: Tue Aug 16, 2022 9:00 am This is already available. We have the Heatflux constraint for this.

Note that W/m² is the flux through a face. The body heat constraint is in W/kg so really for a body, not a face.
It was a typo, I wanted to write that the magnitude is in W/m^3 (or mW/mm^3). The currently available FEM ConstraintHeatflux can be used to apply surface flux in W/m^2 so it would be nice to add body heat flux in W/m^3 (with BF label, as I described in the previous post) for analyses involving CalculiX. The only problem would be making input units consistent for Elmer and CalculiX. Maybe specification in W could be a solution.
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Re: "Constraint Body Heat Source" implemented yet?

Post by Jee-Bee »

uwestoehr wrote: Tue Aug 16, 2022 9:00 am I don't agree that we need special handling for constraints that are not available for all solvers. We have meanwhile proper Wiki pages describing the constraints. FEM requires some reading how it works.
I don't complete agree on this. In general i think the tools should help the user as much as possible. When i come as a new user to FC and i want to do a FEM analysis I don't want to figure out what analyses are possible for what solver. I just want to do a Analysis. When buttons are greyed out based on the chosen solver it is directly clear what constraints can be used and what not.
On the other hand i don't like that there are constraints that are not written down. As example When using CCX and run a Frequency analysis Forces are ignored while with a small tweak it is perfectly valid to run a Frequency analysis with forces applied. So in the latter case is more that constraints require a special solver...
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Re: "Constraint Body Heat Source" implemented yet?

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Jee-Bee wrote: Tue Aug 16, 2022 9:51 am I don't complete agree on this. In general i think the tools should help the user as much as possible. When i come as a new user to FC and i want to do a FEM analysis I don't want to figure out what analyses are possible for what solver. I just want to do a Analysis. When buttons are greyed out based on the chosen solver it is directly clear what constraints can be used and what not.
Right, greyed-out buttons would be a good idea but if they can't be added, I think that there should be at least a warning message. That's what professional FEM software does too. It won't let users submit analyses with unsupported features or at least warn them about it. FreeCAD spits lots of (not always so important) warnings in the Report window so adding warnings for unsupported constraints shouldn't be problematic. A pop-up window would be even better in this case though.

Jee-Bee wrote: Tue Aug 16, 2022 9:51 am with a small tweak it is perfectly valid to run a Frequency analysis with forces applied.
What kind of tweak do you mean (other than preceding static step with preload) ?
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

NewJoker wrote: Tue Aug 16, 2022 9:25 am It was a typo, I wanted to write that the magnitude is in W/m^3 (or mW/mm^3).
We could add a second property to the body heat constraint that accepts inputs as W/m³. Since we know the volume of the boy and its density, we can calculate the values into each other.
However, there are more pressing things for me at the moment.
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Re: "Constraint Body Heat Source" implemented yet?

Post by uwestoehr »

Jee-Bee wrote: Tue Aug 16, 2022 9:51 am I just want to do a Analysis. When buttons are greyed out based on the chosen solver it is directly clear what constraints can be used and what not.
You cannot "just do" an analysis. You first need to learn the workflow. The 3 different solvers we support have each a very different work flow. Then of course you need to learn what properties to set to get a sensible analysis result.

Greying out is not possible because you can use different solvers in one analysis. Personally for thermomech I have Elmer and CCX to check the results of each. At the time I add a constraint it is unknown what solver i will later execute.
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Re: "Constraint Body Heat Source" implemented yet?

Post by NewJoker »

uwestoehr wrote: Tue Aug 16, 2022 10:58 am We could add a second property to the body heat constraint that accepts inputs as W/m³. Since we know the volume of the boy and its density, we can calculate the values into each other.
However, there are more pressing things for me at the moment.
This would be nice but especially if support for this constraint in use with CalculiX was also added.

uwestoehr wrote: Tue Aug 16, 2022 10:58 am However, there are more pressing things for me at the moment.
Sure, there's still a lot to improve in the FEM workbench. I can create a feature request for this so that it doesn't get forgotten.
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