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 The information provided may be out of date.

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Units in COMSOL - Problems

Posted 19.12.2011, 18:11 GMT-5 Version 4.0 4 Replies

Mauricio Flores
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Today I found what seems to be a flaw in COMSOL 4.0. I declared a parameter "h" (planck's constant) and put the following expression (I copy/pasted it here:)

6.62*10^-34 [m^2*kg/s]

Then, I declared parameter "test" as

h

So, I would expect both "test" and "h" to have the same units, but instead, "test" has units "m" (meters). Why does this happen? I am not quite trusting COMSOL on units anymore, unless I made a terrible mistake. Could someone help me?
4 Replies Last Post 17.01.2012, 02:50 GMT-5
John H.
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Posted: 1 decade ago 20.12.2011, 02:39 GMT-5
You should generally avoid variable or parameter names that are predefined by Comsol, such as h (for the mesh element size) and test (for the test operator). Once you rename "h" to something else, it should work as expected. Note that Comsol also predefines some physical constant, and you can refer to Planck's constant as "h_const".
You should generally avoid variable or parameter names that are predefined by Comsol, such as h (for the mesh element size) and test (for the test operator). Once you rename "h" to something else, it should work as expected. Note that Comsol also predefines some physical constant, and you can refer to Planck's constant as "h_const".
Mauricio Flores
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Posted: 1 decade ago 21.12.2011, 15:44 GMT-5
Thanks! That fixes the problem :)
Thanks! That fixes the problem :)
Mauricio Flores
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Posted: 1 decade ago 16.01.2012, 22:27 GMT-5
Where can I find a complete list of physical quantities predefined in COMSOL? I mean, like h_const for Planck's constant.
Where can I find a complete list of physical quantities predefined in COMSOL? I mean, like h_const for Planck's constant.
John H.
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Posted: 1 decade ago 17.01.2012, 02:50 GMT-5
You'll find a list in the Comsol User's Guide: table 3.5, page 123 in version 4.2a.
You'll find a list in the Comsol User's Guide: table 3.5, page 123 in version 4.2a.

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