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Questions about the usage of the operators "down" and "up"

Posted Feb 7, 2011, 3:56 p.m. EST Parameters, Variables, & Functions Version 4.0 4 Replies

Xiaoyi Yu
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Details please see the attachment, because I need some pictures to help description, thank you!

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4 Replies Last Post Feb 8, 2011, 10:11 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 7, 2011, 4:23 p.m. EST
Hi

there are a few things I do not understand in your model. If you have "continuity" on the interiour boundary, which is the default in "union" mode, then the heat flux from left to right and from right to left are by "design" the same. That is the way COMSOL is set up. Now you might add a "thin" surface layer with specific properties too see the doc.

--
Good luck
Ivar
Hi there are a few things I do not understand in your model. If you have "continuity" on the interiour boundary, which is the default in "union" mode, then the heat flux from left to right and from right to left are by "design" the same. That is the way COMSOL is set up. Now you might add a "thin" surface layer with specific properties too see the doc. -- Good luck Ivar
Xiaoyi Yu
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Posted: 1 decade ago Feb 7, 2011, 9:07 p.m. EST

Hi

there are a few things I do not understand in your model. If you have "continuity" on the interiour boundary, which is the default in "union" mode, then the heat flux from left to right and from right to left are by "design" the same. That is the way COMSOL is set up. Now you might add a "thin" surface layer with specific properties too see the doc.

--
Good luck
Ivar


Thank you, Ivar
The heat flux is different, because there is an fixed temperature on the interior boundary, I think the heat flux on the left should be zero because of no temperature gradient, but on the right it should not be zero, since there exists a temperature gradient. This is my opinion.
[QUOTE] Hi there are a few things I do not understand in your model. If you have "continuity" on the interiour boundary, which is the default in "union" mode, then the heat flux from left to right and from right to left are by "design" the same. That is the way COMSOL is set up. Now you might add a "thin" surface layer with specific properties too see the doc. -- Good luck Ivar [/QUOTE] Thank you, Ivar The heat flux is different, because there is an fixed temperature on the interior boundary, I think the heat flux on the left should be zero because of no temperature gradient, but on the right it should not be zero, since there exists a temperature gradient. This is my opinion.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 8, 2011, 4:17 a.m. EST
Hi

but if you are applying continuous boundary conditions one one side and constant temperature on an interiour boundary, you need to bring energy in, and for my that violates the continuity conditions, so you have BC with opposed behaviour. I would rather use an assembly then and say that my internal BC is a special wall and trat left and right side differently, then with a constant T, you have then a three directional energy flow

--
Good luck
Ivar
Hi but if you are applying continuous boundary conditions one one side and constant temperature on an interiour boundary, you need to bring energy in, and for my that violates the continuity conditions, so you have BC with opposed behaviour. I would rather use an assembly then and say that my internal BC is a special wall and trat left and right side differently, then with a constant T, you have then a three directional energy flow -- Good luck Ivar
Xiaoyi Yu
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Posted: 1 decade ago Feb 8, 2011, 10:11 a.m. EST

Hi

but if you are applying continuous boundary conditions one one side and constant temperature on an interiour boundary, you need to bring energy in, and for my that violates the continuity conditions, so you have BC with opposed behaviour. I would rather use an assembly then and say that my internal BC is a special wall and trat left and right side differently, then with a constant T, you have then a three directional energy flow

--
Good luck
Ivar


Thank you! Ivar
Yes, the interior boundary has its own special behavior, i.e., melting.
[QUOTE] Hi but if you are applying continuous boundary conditions one one side and constant temperature on an interiour boundary, you need to bring energy in, and for my that violates the continuity conditions, so you have BC with opposed behaviour. I would rather use an assembly then and say that my internal BC is a special wall and trat left and right side differently, then with a constant T, you have then a three directional energy flow -- Good luck Ivar [/QUOTE] Thank you! Ivar Yes, the interior boundary has its own special behavior, i.e., melting.

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