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Problem with interpolation function and variable

Posted 9 lug 2013, 05:36 GMT-4 Heat Transfer & Phase Change, Materials Version 4.2a 2 Replies

Nicolas M
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Hi !

I'm a beginner in COMSOL 4.2a and I'm trying to simulate a model using the Microwave Heating interface.
I have to consider the temperature dependance for the thermal conductivity and the electrical conductivity.
For now, I just create an interpolation function, named "func1", which has only one argument (temperature)
and giving the corresponding thermal conductivity.

I also define a variable "var1" to create a link with the function, and I use it as a value of the thermal conductivity.

But after simulation, I get this message :

Failed to evaluate variable Jacobian
- Variable : T
- Geometry : 1
- Domain : 1

The domain 1 is a material using the variable "var1" as thermal conductivity.

Does anyone know how to solve this problem ? Thanks in advance.

Nicolas.

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2 Replies Last Post 11 lug 2013, 08:15 GMT-4
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago 11 lug 2013, 04:03 GMT-4
Hi,

I can see two problems here:

- The dependent variable name for temperature in the Microwave Heating physics is T2 and not T (probably because the model at some point included some other heat transfer physics that defined a temperature T). You can rename T2 as T under Dependent Variables in the Microwave Heating node's settings window.

- The variable var1 is defined as a global variable, where T is not recognized as the variable for temperature because it is defined as a temperature field in the geometry in Model 1. If you instead define the variable under Model 1>Definitions, it will recognize T and you will not see the orange color that indicates a problem with the variable (the tooltip says "Unknown variable T"). It is possible to refer to T also on the global level, but you must then use the syntax mod1.T.

Best regards,
Magnus Ringh, COMSOL
Hi, I can see two problems here: - The dependent variable name for temperature in the Microwave Heating physics is T2 and not T (probably because the model at some point included some other heat transfer physics that defined a temperature T). You can rename T2 as T under Dependent Variables in the Microwave Heating node's settings window. - The variable var1 is defined as a global variable, where T is not recognized as the variable for temperature because it is defined as a temperature field in the geometry in Model 1. If you instead define the variable under Model 1>Definitions, it will recognize T and you will not see the orange color that indicates a problem with the variable (the tooltip says "Unknown variable T"). It is possible to refer to T also on the global level, but you must then use the syntax mod1.T. Best regards, Magnus Ringh, COMSOL
Nicolas M
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Posted: 1 decade ago 11 lug 2013, 08:15 GMT-4
Hi !

Thank you very much, this solves my problem. Now it's working !

Best regards,

Nicolas.
Hi ! Thank you very much, this solves my problem. Now it's working ! Best regards, Nicolas.

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