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The second argument of the d() operator must be a variable name.

Posted Aug 25, 2011, 11:01 a.m. EDT Studies & Solvers Version 4.2, Version 4.2a 7 Replies

Leanne Nixon
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For two of the models that I'm trying to run I keep getting the following error:

"The second argument of the d() operator must be a variable name."

I do not understand what that means, and I cannot find anywhere how to try and fix the problem.

Any suggestions?

Thanks!
7 Replies Last Post Jan 11, 2012, 5:18 a.m. EST
COMSOL Moderator

Hello Leanne Nixon

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Marjan
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Posted: 1 decade ago Dec 6, 2011, 9:37 a.m. EST
Hi,
I also have the same problem in 4.2.a version. Any suggestion? I am using structural mechanics module.

Marjan
Hi, I also have the same problem in 4.2.a version. Any suggestion? I am using structural mechanics module. Marjan
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago Dec 6, 2011, 10:27 a.m. EST
Hi,

Make sure that all differentiation operators in the model have valid variable names as their second argument (the variable that you differentiate with respect to). For example,

d(x*y,x)

is valid but

d(x*y,1) or d(x*y,2*x)

give the error that you report.

Best regards,
Magnus Ringh, COMSOL
Hi, Make sure that all differentiation operators in the model have valid variable names as their second argument (the variable that you differentiate with respect to). For example, d(x*y,x) is valid but d(x*y,1) or d(x*y,2*x) give the error that you report. Best regards, Magnus Ringh, COMSOL
Marjan
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Posted: 1 decade ago Dec 6, 2011, 10:48 a.m. EST
Hi again,

Thanks for the reply. I solved it by removing the check mark for nearly in-compressible material. I did not have any analytic function that uses d function.

Yours,
Marjan
Hi again, Thanks for the reply. I solved it by removing the check mark for nearly in-compressible material. I did not have any analytic function that uses d function. Yours, Marjan
Chiwei Ong
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Posted: 1 decade ago Dec 9, 2011, 5:56 a.m. EST
Hi, I am just using 4.2a. and wish to know more about it.

When i formulate the hyperelastic material using Mooney Rivlin material,
the same error pop up.

May I know why Mooney Rivlin material will be involve into problem?
as i use Neo hookean material, all the things done smoothly.
Hi, I am just using 4.2a. and wish to know more about it. When i formulate the hyperelastic material using Mooney Rivlin material, the same error pop up. May I know why Mooney Rivlin material will be involve into problem? as i use Neo hookean material, all the things done smoothly.
Lars Gregersen COMSOL Employee

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Posted: 1 decade ago Dec 9, 2011, 6:41 a.m. EST
Hi

You should try the update for Comsol 4.2a:
www.comsol.com/support/updates

It solves a specific problem with the structural mechanics module that causes this problem.

--
Lars Gregersen
Comsol Denmark
Hi You should try the update for Comsol 4.2a: http://www.comsol.com/support/updates It solves a specific problem with the structural mechanics module that causes this problem. -- Lars Gregersen Comsol Denmark
Chiwei Ong
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Posted: 1 decade ago Dec 9, 2011, 7:00 a.m. EST
Dear Lars Gregersen ,

Thank you.
I will try it on monday,as now do not have comsol in my computer.

will update you all information whether i solve it or not.
Dear Lars Gregersen , Thank you. I will try it on monday,as now do not have comsol in my computer. will update you all information whether i solve it or not.
Peter Varga
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Posted: 1 decade ago Jan 11, 2012, 5:18 a.m. EST
Dear All,

I can confirm that this problem is removed by the Update 2.

Best,
Peter
Dear All, I can confirm that this problem is removed by the Update 2. Best, Peter

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