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Using interpolation tables for temperature dependent structural and themal properties
Posted Dec 13, 2012, 12:50 p.m. EST Heat Transfer & Phase Change, Structural Mechanics Version 4.3 5 Replies
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This will eventually be an analysis of the thermal and structural very steep pulses but for now I am keeping it simple.
(stationary and moderate time dependent loads)
In trying to defining some basic temperature dependent properties (i.e. youngs modulus, poisson's ratio, Cp) by importing txt files of temperature and material property at that temperature I run into a problem.
No matter what variations I try, T comes out as an unknown jacobian variable.
Is there a way of letting COMSOL know that in the interpolation tables T is temperature.
The modules I am using in 4.3 are the Structural (including thermal strain) and the Heat Transfer module.
If this is not possible in there another way of using these tables?
Thanks,
--
Arthur Rupel
(stationary and moderate time dependent loads)
In trying to defining some basic temperature dependent properties (i.e. youngs modulus, poisson's ratio, Cp) by importing txt files of temperature and material property at that temperature I run into a problem.
No matter what variations I try, T comes out as an unknown jacobian variable.
Is there a way of letting COMSOL know that in the interpolation tables T is temperature.
The modules I am using in 4.3 are the Structural (including thermal strain) and the Heat Transfer module.
If this is not possible in there another way of using these tables?
Thanks,
--
Arthur Rupel
5 Replies Last Post Dec 15, 2012, 6:01 a.m. EST
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Posted:
1 decade ago
On looking at the error message upward, under dependent variables stored was mod1.T2 instead of T.
Replacing T with mod1.T2 in the interpolation function label and in the independent variable in the table, the program ran well, showing the temperature dependency of the various material properties upon completion.
I noticed other people were having problems with the interpolation function and temperature dependent material properties. Perhaps this will help.
--
Arthur Rupel
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Posted:
1 decade ago
Hi
but your dependent variable in the physics was it T or T2 ?, if you include several physics each with a dependent variable T, COMSOL will rename the variable for the second and thereacter by T2, T3 ,... Then you must also change the names in your formaulys to T2, T3, ...
--
Good luck
Ivar
but your dependent variable in the physics was it T or T2 ?, if you include several physics each with a dependent variable T, COMSOL will rename the variable for the second and thereacter by T2, T3 ,... Then you must also change the names in your formaulys to T2, T3, ...
--
Good luck
Ivar
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Posted:
1 decade ago
Thanks for advice. Ironically looking at the COMSOL manuals and examples everything said the the temperature variable would be T (for piecewise and analytical functions). Under this guidance I tried every conceivable variation for T and always got undefined jacobian variable.
It was only when I traced the error message upwards that I found undefined variable mod1.T2 which I then replaced for T in my interpolations functions and everything ran smoothly.
The thermal stress options was taken from the Structural Mechanics Module.
But I had to use the HT module for boundary conditions, heating and convection.
This may be something that I have to check since Cp and k are also temperature dependent and are inputed as temperature dependent properties.
If this is true, then it may be that I have to use either a mod1.T1 or are mod1.T3 as the independent variable in HT.
Not sure of this but will try it out.
Also I can plot the Cp and k properties at the elevated tempertures to see if they physically make sense.
Sorry for the longwinded response.
Again thanks,
Art
--
Arthur Rupel
It was only when I traced the error message upwards that I found undefined variable mod1.T2 which I then replaced for T in my interpolations functions and everything ran smoothly.
The thermal stress options was taken from the Structural Mechanics Module.
But I had to use the HT module for boundary conditions, heating and convection.
This may be something that I have to check since Cp and k are also temperature dependent and are inputed as temperature dependent properties.
If this is true, then it may be that I have to use either a mod1.T1 or are mod1.T3 as the independent variable in HT.
Not sure of this but will try it out.
Also I can plot the Cp and k properties at the elevated tempertures to see if they physically make sense.
Sorry for the longwinded response.
Again thanks,
Art
--
Arthur Rupel
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Posted:
1 decade ago
Just a final say from my previous rather wordy discussion.
I plotted Cp and k, and they are in agreement with the temperature distribution and the interpolation tables.
So mod1.T2 did the trick.
PS: Ms. Margareta Muchacha wishes you a Merry Christmas!
--
Arthur Rupel
I plotted Cp and k, and they are in agreement with the temperature distribution and the interpolation tables.
So mod1.T2 did the trick.
PS: Ms. Margareta Muchacha wishes you a Merry Christmas!
--
Arthur Rupel
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Posted:
1 decade ago
Hi
I believe you are getting confused with dependent variables for different physics, that must be unique (T, T1, T2, ...as default by COMSOL if you add several physics with the same dependent variable "temperature", and the dummy variable for functions in general, and finally the variable for the material properties.
Check your dependent variable names in the main physics node, then check that the material propaerties are called with the correet varaible name.
Sometimes COMSOL get confused, when you add and delete several physics and or solvers and your internal data base pointer system to the variables might get corrupt. So if you modify a lot your model, it's often worth, once you are happy (or give up because it seems to not get you anywhere) to rebuild from scratch your model, to be sure you get all default names in their simplest form
--
Good luck
Ivar
I believe you are getting confused with dependent variables for different physics, that must be unique (T, T1, T2, ...as default by COMSOL if you add several physics with the same dependent variable "temperature", and the dummy variable for functions in general, and finally the variable for the material properties.
Check your dependent variable names in the main physics node, then check that the material propaerties are called with the correet varaible name.
Sometimes COMSOL get confused, when you add and delete several physics and or solvers and your internal data base pointer system to the variables might get corrupt. So if you modify a lot your model, it's often worth, once you are happy (or give up because it seems to not get you anywhere) to rebuild from scratch your model, to be sure you get all default names in their simplest form
--
Good luck
Ivar