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Failed to Evaluate Variable Rho

Posted 28 ago 2015, 08:16 GMT-4 Fluid & Heat, Computational Fluid Dynamics (CFD), Microfluidics Version 4.2a 4 Replies

Elizabeth Walker
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Hi,

I'm modeling a 3-layer device (fluid flow/porous membrane/fluid flow) with Free and Porous Media Flow physics in version 4.2a. I'm trying to add the effects of gravity to my model (I've already gotten the study to run without the effects of gravity). I added a volume force in the y direction and used"-g_const*material.rho" as my expression. However, when I run the study, the software tells me that rho is unknown. I've also tried using variations of the "material.rho" part - I've used just "rho" and also "root.material.rho" but both still result in an error saying that rho is unknown. I'm confused by this because rho is clearly defined for both materials used, and when I type the expression in for the volume force, it seems to recognize all of the entered terms.

Does anybody know why this might be happening and what I should do in order to incorporate the effects of gravity in my model, or how I can fix my current expression?

Thank you!
4 Replies Last Post 9 set 2015, 09:59 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 9 years ago 28 ago 2015, 09:59 GMT-4

Elizabeth,

I don't recall how it was exactly in 4.2a, in 5.1 the syntax for a material property is e.g. comp1.mat1.def.rho(T[1/K]).

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Elizabeth, I don't recall how it was exactly in 4.2a, in 5.1 the syntax for a material property is e.g. comp1.mat1.def.rho(T[1/K]). Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Elizabeth Walker
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Posted: 9 years ago 29 ago 2015, 13:41 GMT-4

Elizabeth,

I don't recall how it was exactly in 4.2a, in 5.1 the syntax for a material property is e.g. comp1.mat1.def.rho(T[1/K]).

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com


Hi Edgar,

I really appreciate your response; however, this syntax doesn't seem to work with v4.2a. When I enter comp1.mat1.def.rho(T[1/K]) into the volume force node, first I am told that T and K are not recognized, then when I try to run it says that the whole 'comp1.mat1.def.rho' isn't recognized. Do you have any other tips for me?

Thank you
[QUOTE] Elizabeth, I don't recall how it was exactly in 4.2a, in 5.1 the syntax for a material property is e.g. comp1.mat1.def.rho(T[1/K]). Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com [/QUOTE] Hi Edgar, I really appreciate your response; however, this syntax doesn't seem to work with v4.2a. When I enter comp1.mat1.def.rho(T[1/K]) into the volume force node, first I am told that T and K are not recognized, then when I try to run it says that the whole 'comp1.mat1.def.rho' isn't recognized. Do you have any other tips for me? Thank you
Edgar J. Kaiser Certified Consultant
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Posted: 9 years ago 31 ago 2015, 04:14 GMT-4
Elizabeth,

unfortunately I don't have a version 4 installation running here any more. You have to find out the proper syntax. Check the tags COMSOL shows you along the model tree. You may have to switch that on in the preferences. Then build up the identifier along those tags.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Elizabeth, unfortunately I don't have a version 4 installation running here any more. You have to find out the proper syntax. Check the tags COMSOL shows you along the model tree. You may have to switch that on in the preferences. Then build up the identifier along those tags. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Elizabeth Walker
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Posted: 9 years ago 9 set 2015, 09:59 GMT-4
Hi Edgar,

I cannot seem to find these tags or the option to switch them on in the preferences - could you please provide further guidance if possible?

Thank you.
Hi Edgar, I cannot seem to find these tags or the option to switch them on in the preferences - could you please provide further guidance if possible? Thank you.

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