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Temperature dependent variables - Circular variable dependency detected.

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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 22 juin 2011, 21:47 UTC−4

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Posted: 1 decade ago 18 mai 2011, 22:25 UTC−4
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.

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Posted: 1 decade ago 19 mai 2011, 03:08 UTC−4
Thx, thats it. :)
Thx, thats it. :)

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Posted: 1 decade ago 22 juin 2011, 21:47 UTC−4
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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