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Old   August 5, 2008, 15:29
Default Defining non-constant material properties
  #1
Scott
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I have a solid domain defined in my model. The solid material (AlN) has a thermal conductivity that varies significantly within the temperature ranges of my model. Is it possible to define a material in CFX with a lookup table for thermal conductivity? I looked at many material definition examples in the CCL and RGP formats, but I haven't seen anything applicable. Any ideas? Thanks in advance!
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Old   August 5, 2008, 16:19
Default Re: Defining non-constant material properties
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Rogerio Fernandes Brito
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Yes, itīs possible and itīs so easy! Send me your file name.cfx (and name.ccl) and i will help you, Sir.

rogeriobrito2007@hotmail.com

Best,
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Old   August 5, 2008, 16:20
Default Re: Defining non-constant material properties
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Rogerio Fernandes Brito
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donīt forget to send me the expression of your variation of the temperature.

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Old   August 5, 2008, 16:53
Default Re: Defining non-constant material properties
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Scott
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Unfortunately I'm unable to email or post my work. Perhaps you can just point me in the right direction, reference a help file, or paste some CCL code in a reply to this forum thread? Thanks!
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Old   August 6, 2008, 07:14
Default Re: Defining non-constant material properties
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Rogerio Fernandes Brito
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Hi Sir Mr. Scott,

Create a CEL expression like that:

Fluxoa (B*(19453.29701*(t/A)^3.07678)/(4.73947^3.07678+(t/A)^3.07678))

A 1.0 [s] B 1.0 [W m^-2]

where "Fluxoa" is my heat flux in [W m^-2] as my boundary condition. You could create a new material for your fluid with your density in function of the temperature.

Best,
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Old   August 7, 2008, 06:18
Default Re: Defining non-constant material properties
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Josh
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hi, Scott,

I have the same problem in my simulation. currently i am using the functions which are fitted by myself.

this is a compromising approch with certain errors, nevertheless it is the only way, as i know, to define your own properties without the table generating software.
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Old   August 8, 2008, 14:36
Default Re: Defining non-constant material properties
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Scott
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Indeed, I took the same approach. I'll document the process I took, for the benefit of others who might have the same question...

First, I created a user function (1D interpolation) for each temperature-dependent material property. I imported the material property data tables (as text files) into the function definitions. Then I made expressions for each function and set the value of the expression equal to the output of the function, with temperature as the function argument. In the material property definition, I set the applicable material properties (e.g. thermal conductivity) to the corresponding expressions. I actually did this for a number of different solid materials that I commonly use, and then exported the materials/user-functions/expressions as a CCL file so I can easily load the detailed material definitions on subsequent models.
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Old   August 8, 2008, 17:35
Default Re: Defining non-constant material properties
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Rogerio Fernandes Brito
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Could you send me your file (.cxf, and .ccl)? I would like to see, because iīm working in a problem like that. Thanks

My e-mail is: rogeriobrito2007@hotmail.com

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