Menu

Discussion Forum

New Discussion
查找

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Failed to Evaluate Variable Rho

Posted 2015年8月28日 GMT-4 08:16 Fluid & Heat, Computational Fluid Dynamics (CFD), Microfluidics Version 4.2a 4 Replies

Elizabeth Walker
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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 2015年9月9日 GMT-4 09:59
Edgar J. Kaiser Certified Consultant
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2015年8月28日 GMT-4 09:59

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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2015年8月29日 GMT-4 13:41

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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2015年8月31日 GMT-4 04:14
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 2015年9月9日 GMT-4 09:59
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.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content