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Temperature dependent variables - Circular variable dependency detected.

Posted May 18, 2011, 12:24 p.m. EDT Parameters, Variables, & Functions Version 4.1 3 Replies

Kai Feldhusen
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Hello folks,

I would like to define some temperature-dependent variables in my model. I defined them under "Global definitions - variables". So Comsol shall calculate for each time step the variable with the current temperature.
For example:

Name: E
Expression: 500*T - 200 [Pa]

I thought, that Comsol know that he has to use the temperature for "T", but I got an error message:

Circular variable dependency detected.
- Variable: T
- Geometry: 1
- Domain: 1

Can anyone help me?

Greetings.
3 Replies Last Post Jun 22, 2011, 9:47 p.m. EDT
Francois Gregoire
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Posted: 1 decade ago May 18, 2011, 10:25 p.m. EDT
Hi,

Try this:

(500*mod1.T[1/K]-200)[Pa]

[1/K] is there to cancel the units of temperature.

Hi, Try this: (500*mod1.T[1/K]-200)[Pa] [1/K] is there to cancel the units of temperature.
Kai Feldhusen
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Posted: 1 decade ago May 19, 2011, 3:08 a.m. EDT
Thx, thats it. :)
Thx, thats it. :)
Ali Saad
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Posted: 1 decade ago Jun 22, 2011, 9:47 p.m. EDT
Hi,

Since you are defining a global variable, you should point to the model to which it belongs. In your case, T is the dependent variable for model 1 (your only model I presume), that is why calling this variable requires: mod1.T, where mod1 is your model's identifier.

If the same variable is used in a subdomain field (variables under model 1), you could ommit the pointer mod1 and just use the variable T

Regards
--
Ali
Hi, Since you are defining a global variable, you should point to the model to which it belongs. In your case, T is the dependent variable for model 1 (your only model I presume), that is why calling this variable requires: mod1.T, where mod1 is your model's identifier. If the same variable is used in a subdomain field (variables under model 1), you could ommit the pointer mod1 and just use the variable T Regards -- Ali

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