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a very basic question

Posted May 4, 2011, 8:00 a.m. EDT Version 4.1 8 Replies

Naveed Akhtar
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Hi

I am moving from COMSOL 3.5a to 4.1. I was using PDE (General form) in which "h" and "p" are two variables. One of the parameter say "gamma" is dependent on "h". When I define "gamma" as a function of "h" in "variables", it becomes red and the solution says cannot evaluate "h".

Before in COMSOL, I was easily defining "h" in scalar or global expressions and had never faced any problems. But in 4.1, this does not accept in "variables".

There must be another way to define "gamma" as a function of "h", elsewhere. Does anybody know?

Thanks
8 Replies Last Post May 5, 2011, 9:19 a.m. EDT
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago May 4, 2011, 8:15 a.m. EDT
In COMSOL, "h" is the mesh element size.It's a bad idea to try and use the same name for one of your variables. Try some other, less common, name for your variables.
In COMSOL, "h" is the mesh element size.It's a bad idea to try and use the same name for one of your variables. Try some other, less common, name for your variables.
Naveed Akhtar
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Posted: 1 decade ago May 4, 2011, 8:37 a.m. EDT
Hi,

I used "hh" instead, but the problem remains. In comsol 3.5a, it is working fine. Any idea?

regards
Hi, I used "hh" instead, but the problem remains. In comsol 3.5a, it is working fine. Any idea? regards
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago May 4, 2011, 8:47 a.m. EDT
Hard to say much of any value without seeing your file. One possibility is that your hh is defined for one Model but that you are trying to use it in a definition at the global level (i.e. in your Global Definitions), which of course won't work. If that's the case, try using Definitions inside the model where the independent variables are defined instead.
Hard to say much of any value without seeing your file. One possibility is that your hh is defined for one Model but that you are trying to use it in a definition at the global level (i.e. in your Global Definitions), which of course won't work. If that's the case, try using Definitions inside the model where the independent variables are defined instead.
Naveed Akhtar
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Posted: 1 decade ago May 4, 2011, 9:06 a.m. EDT
Hi

I attached the file. Perhaps you have an idea by looking at variables and PDE eqn.

Regards
Hi I attached the file. Perhaps you have an idea by looking at variables and PDE eqn. Regards

Attachments:

Francois Gregoire
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Posted: 1 decade ago May 4, 2011, 9:10 a.m. EDT
Salut Naveed

If you have defined your variable or your parameter under Global Definitions, you have to type the Model Identifier before h (mod1.h).

If you have defined h under Model 1, then I don't know what to tell you.

look at the attached jpg.
Salut Naveed If you have defined your variable or your parameter under Global Definitions, you have to type the Model Identifier before h (mod1.h). If you have defined h under Model 1, then I don't know what to tell you. look at the attached jpg.

Attachments:

Francois Gregoire
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Posted: 1 decade ago May 4, 2011, 9:12 a.m. EDT

If you have defined h under Model 1, then I don't know what to tell you.


If you have defined GAMMA under Model 1...
[QUOTE] If you have defined h under Model 1, then I don't know what to tell you. [/QUOTE] If you have defined GAMMA under Model 1...
Naveed Akhtar
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Posted: 1 decade ago May 4, 2011, 9:16 a.m. EDT
Thank you very much! Yes, it was missing "mod1". I have never done this in COMSOL 3.5a, so a new thing to learn.

Thank you very much, indeed.

Regards
Naveed
Thank you very much! Yes, it was missing "mod1". I have never done this in COMSOL 3.5a, so a new thing to learn. Thank you very much, indeed. Regards Naveed
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 5, 2011, 9:19 a.m. EDT
Hi

also a little warning, use names with more than 1 lettre, as most of the single letter are already used by COMSOL,and it's quickly done to mix and change internal variables, this is allowed though, when you know what you are doing ;)

--
Good luck
Ivar
Hi also a little warning, use names with more than 1 lettre, as most of the single letter are already used by COMSOL,and it's quickly done to mix and change internal variables, this is allowed though, when you know what you are doing ;) -- Good luck Ivar

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