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Unable to call the local function defined when defining material properties

Posted 26.07.2018, 17:39 GMT-4 Heat Transfer & Phase Change, Heat Transfer, Parameters, Variables, & Functions Version 5.3 2 Replies

Shengyue Shan
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Hello,

I am new to COMSOL, and I ran into problems when I am defining material properties. I defined analytic functions and piecewise functions under Component 1 ==> Definitions, and then while I am trying to define the properties, I put the name of the function that I have already defined in the Expression box, but a floating box with "Unknow variable" appears everytime. And I also tried right click on Basic ==> Funcitions to define the variable that I would like to use as the property expression but the same thing happens.

I really would like to know why all the variable that I defined as functions cannot be called later on. But I have to define them as functions because they are temperature dependent and I have to put "if" condition for them because the expression is different under different temperatures.

I would appreciate any help! Thank you very much!

Best regards, Shengyue Shan

2 Replies Last Post 27.07.2018, 11:43 GMT-4
Nichal Gentilal
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Posted: 6 years ago 27.07.2018, 04:48 GMT-4

Hi Shengyue,

When you use the function you define in the material properties are you specifying the dependent variable?

If your density is a function that you previously defined and is temperature depedent you have to use the_name_of_your_function(T) instead of just the_name_of_your_function

Hope this helps.

Best, Nichal

Hi Shengyue, When you use the function you define in the material properties are you specifying the dependent variable? If your density is a function that you previously defined and is temperature depedent you have to use the_name_of_your_function(T) instead of just the_name_of_your_function Hope this helps. Best, Nichal
Shengyue Shan
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Posted: 6 years ago 27.07.2018, 11:43 GMT-4

Hi Shengyue,

When you use the function you define in the material properties are you specifying the dependent variable?

If your density is a function that you previously defined and is temperature depedent you have to use the_name_of_your_function(T) instead of just the_name_of_your_function

Hope this helps.

Best, Nichal

Hi Nichal,

I know that you mentioned it in the last answer you gave to me, and I tried but it did not work. But today I tried it again and I figured out why! Because some of the functions that I used to define my material properties are also defined by another variables, so I have to add all the variables in the parentheses.

Thank you very much for your help!!!

Best regards, Shengyue Shan

>Hi Shengyue, > >When you use the function you define in the material properties are you specifying the dependent variable? > >If your density is a function that you previously defined and is temperature depedent you have to use the_name_of_your_function(T) instead of just the_name_of_your_function > >Hope this helps. > >Best, >Nichal Hi Nichal, I know that you mentioned it in the last answer you gave to me, and I tried but it did not work. But today I tried it again and I figured out why! Because some of the functions that I used to define my material properties are also defined by another variables, so I have to add all the variables in the parentheses. Thank you very much for your help!!! Best regards, Shengyue Shan

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