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Material properties on a boundary

Posted Aug 15, 2011, 4:08 a.m. EDT Materials, Parameters, Variables, & Functions Version 4.2, Version 5.2 4 Replies

Michael Welland
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Hi everyone,

I am using the physics builder interface make my own heat transfer mode and would like to include the emissivity for radiative heat loss. Everything works fine with my heat balance correctly accessing my materials (also with customized material groups) on the selected *domain*, except for the emissivity. The solver returns an error that it cannot find the parameter and, if I look at the materials node, I see that boundaries 1-4 require a material (despite the fact that the domain enclosed by these boundaries does have the material.

I saw a previous thread where Ivar commented:
" As by default in COMSOL the boundaries do NOT heritage the domain material properties, particularly because in "union" mode, you have a common boundary for two adjacent domains, so COMSOL cannot choose by itself which of the two materials to set on the common boundary between the two materials.
"

This makes sense to me (nicely pointed out!), but I wonder if there is an alternative to the default which may be enabled? There are a number of workarounds (the simplest of which being including the material again, this time on the boundaries) but it strikes me as sloppy.

Anyone have any suggestions?

Thanks!
4 Replies Last Post Sep 5, 2017, 12:03 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 17, 2011, 2:06 a.m. EDT
Hi

I'm not sure I catch all, but

Have you tried to define a second material node (same material as the bulk) and apply them to the boundaries ?

Or you might specify a boundary material property manually in the boundary physics node

--
Good luck
Ivar
Hi I'm not sure I catch all, but Have you tried to define a second material node (same material as the bulk) and apply them to the boundaries ? Or you might specify a boundary material property manually in the boundary physics node -- Good luck Ivar

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Michael Welland
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Posted: 1 decade ago Aug 18, 2011, 5:22 a.m. EDT
Yes, I did that to make it work, but it seems sloppy and silly to have to say that the boundary is the same material as the domain. I was hoping for a more elegant alternative.
For example, on the heat transport mode, you select a material for a domain but you can add a boundary condition such as 'surface to ambient radiation', which uses the emissivity of the material. Therefore, it looks like the material which is on the domain level, is still accessible on the boundary level.
Yes, I did that to make it work, but it seems sloppy and silly to have to say that the boundary is the same material as the domain. I was hoping for a more elegant alternative. For example, on the heat transport mode, you select a material for a domain but you can add a boundary condition such as 'surface to ambient radiation', which uses the emissivity of the material. Therefore, it looks like the material which is on the domain level, is still accessible on the boundary level.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 18, 2011, 6:23 a.m. EDT
Hi
What I have heard (to be confirmed) COMSOL is working on this for a future release ;)

--
Good luck
Ivar
Hi What I have heard (to be confirmed) COMSOL is working on this for a future release ;) -- Good luck Ivar
Fareeha Hameed
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Posted: 7 years ago Sep 5, 2017, 12:03 p.m. EDT
I assigned materials to the boundaries and then I got the error that the corresponding domains needed a material
I assigned materials to the boundaries and then I got the error that the corresponding domains needed a material

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