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August 30, 2015, 03:12 
Conductivity as a vector value

#1 
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Nurzhan
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Hi Guys,
I am trying to set a thermal conductivity as a full tensor so it varies based on one of the directions (X, Y, and Z). In order to set a magnitude of the conductivity, I looked at material properties and changed the magnitude there. However, my conductivity is described by three functions of temperature, each function per direction. I believe there is an easy way to do it, but I am failing to find the solution. Could you please help me? Cheers, Nurzhan Last edited by Nurzhan; August 31, 2015 at 04:50. 

August 30, 2015, 06:27 

#2 
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Glenn Horrocks
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Use a CEL expression, interpolation function or junction box rountine.


August 30, 2015, 15:28 

#3 
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Based on the mathematical formalism for heat conduction, thermal conductivity cannot be a vector. It is a second order tensor, that for isotropic materials reduces to scalar.
In the case of anisotropic thermal conduction, ANSYS CFX has a hidden feature to input the orthotropic conductivities (principal values on a specific orientation of the material) , or the full tensor. You can search this forum for "Thermal Conductivity X".. Otherwise, you should probably contact ANSYS CFX support for help. Either of those values can be set using CEL expression, interpolation functions or via user Fortran junction boxes. 

August 30, 2015, 17:50 

#4 
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Nurzhan
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Thank you very much for your responses!
Cheers, Nurzhan 

August 31, 2015, 03:05 

#5 
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Nurzhan
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Hi Glenn/Opaque,
I managed to set thermal conductivity as a full tensor using CEL as you advised me. However, the same way does not work for electrical conductivity. The error looks like that: ERROR CCL validation failed with message: Error: Invalid Option parameter 'Orthotropic Cartesian Components' Any ideas how to get over this problem? The feeling is like ANSYS intentionally stopping people to use electrical conductivity as a vector value. What do you think? Thank you in advance! Nurzhan Last edited by Nurzhan; August 31, 2015 at 04:50. 

August 31, 2015, 03:23 

#6 
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Glenn Horrocks
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Thermal conductivity is not a vector. Opaque explained that very well.
As the anisotropic thermal conductivity is a hidden feature that means it is not a supported feature. This means it has not completed all testing, may not be accurate or correctly implemented. For many of these cases it is because the introduction of this additional flexibility introduces additional terms into the modelled equations which CFX does not model. It is then user beware when you decide to use them. So no, it is unlikely that ANSYS has removed anisotropic electrical conductivity. Why would they develop it then remove it? What is far more likely is that it can introduce additional difficulties into the modelled equations and CFX has not got a model to handle that yet. 

September 3, 2015, 00:06 

#7  
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Nurzhan
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Quote:
I used your suggestion to set thermal conductivity for an anisotropic material, using an orthotropic coordinates option (shown below), it worked for me. Thanks! THERMAL CONDUCTIVITY: Option = Orthotropic Cartesian Components Thermal Conductivity X Component= # [W m^1 K^1] Thermal Conductivity Y Component= # [W m^1 K^1] Thermal Conductivity Z Component= # [W m^1 K^1] END However, I tried to use the same method to set electrical conductivity for an anisotropic material, and it didn't work. Do you have any idea how to handle this problem? Thanks in advance, Nurzhan 

September 3, 2015, 17:45 

#8 
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Glenn Horrocks
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I do not think CFX can handle anisotropic electrical conductivity. Don't forget the anisotropic thermal conductivity is just a beta feature so is not fully supported.


September 3, 2015, 19:41 

#9 
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There are hidden ways to access the anisotropic diffusion model for several equations. If you contact ANSYS CFX, they can provide you with the following beta reconfiguration of the electrical conductivity settings:
Code:
RULES: SINGLETON: ELECTRICAL CONDUCTIVITY Description = Hold the details for an advanced description of \ Electrical Conductivity. Solver Name = CONELEC Context Rule = Option Essential Parameter List = Option Allowed Option List = \ Value, \ Orthotropic Cartesian Components CONTEXT: Value Essential Parameter List = \ Electrical Conductivity END CONTEXT: Orthotropic Cartesian Components Essential Parameter List = \ Electrical Conductivity X Component, \ Electrical Conductivity Y Component, \ Electrical Conductivity Z Component END END PARAMETER: Electrical Conductivity X Component Parameter Type = Real Quantity Type = Electrical Conductivity Dynamic Reread Item = Yes Solver Name = CONELEC1 Group Membership = VECTOR, CONELEC, 1 END PARAMETER: Electrical Conductivity Y Component Parameter Type = Real Quantity Type = Electrical Conductivity Dynamic Reread Item = Yes Solver Name = CONELEC2 Group Membership = VECTOR, CONELEC, 2 END PARAMETER: Electrical Conductivity Z Component Parameter Type = Real Quantity Type = Electrical Conductivity Dynamic Reread Item = Yes Solver Name = CONELEC3 Group Membership = VECTOR, CONELEC, 3 END END Code:
cfx5solve def MyAnisoCase.def ccl aniso_eleccon.ccl ..... 

September 3, 2015, 23:50 

#10 
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Nurzhan
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Thank you, guys! I do not know how to express my feelings right now  I really appreciate your help.
Regards, Nurzhan 

September 30, 2015, 20:58 

#11  
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Nurzhan
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Hi Opaque,
I have been trying to apply the additional rules, written above to my simple simulation. However, I get an error saying that there is an "Error reading Command Language data from memory". I tried my simulation without the additional rules and the simulation worked fine. I decided to describe the procedure of my simulation below. 1) Setting all paramters in cfx pre (electrical conductivity specified as isotropic) and cube.def file is created: Quote:
However, when I apply the additional rules (a ccl file, named aniso_eleccon.ccl) Quote:
Quote:
I run all three codes using through the command line Quote:
Quote:
Thanks for taking your time to read this. Regards, Nurzhan 

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