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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 The information provided may be out of date.

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Global parameters vs. Model/Definitions/Variables

Posted 2012年11月13日 GMT-5 05:42 Geometry, Parameters, Variables, & Functions Version 4.0 3 Replies

Kamil Dursun
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It seems that the geometry can only be defined by global parameters while the rest of the modeling can also use variables.
Is there a way to access the model variables in the geometry such as mod1.Definitions.Params1.xab where xab is a variable that belong to Params1 in variables?
Thanks in advance.
Kamil
3 Replies Last Post 2012年11月14日 GMT-5 02:44
Jesus Lucio
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Posted: 1 decade ago 2012年11月13日 GMT-5 12:29
Hello, Kamil,

I see it this way: it seems that Geometry only accepts Parameters (they are only available as Global Definitions), not Variables (may they be Global or Model-scope). You can see that neither a Global Variable is accepted in the Geometry.

Jesus.
Hello, Kamil, I see it this way: it seems that Geometry only accepts Parameters (they are only available as Global Definitions), not Variables (may they be Global or Model-scope). You can see that neither a Global Variable is accepted in the Geometry. Jesus.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2012年11月13日 GMT-5 14:43
Hi

but parameters can be changed with the "external Parametric sweep node" and then you adapt your geoemtry and can solve for different Parameter values

--
Good luck
Ivar
Hi but parameters can be changed with the "external Parametric sweep node" and then you adapt your geoemtry and can solve for different Parameter values -- Good luck Ivar
Andrea Ferrario COMSOL Employee

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Posted: 1 decade ago 2012年11月14日 GMT-5 02:44
Hello Kamil,

Jesus is right: only "model parameters" (the ones in the Parameters node) can be used in the construction of the geometry. The reason is that those parameters have always a fixed value each time you solve (or at each step of a sweep). "Variables", instead, can be defined using almost anything: you can have a variable that depends on the solution and that cannot be used to construct the geometry directly.

If you need to solve problems such as "find the right dimension so that a certain condition is met", you need to follow Ivar's advice and perform a parametric sweep, or use optimization (if you have the required module).

--
Andrea Ferrario
Electromagnetics Group
COMSOL AB
Hello Kamil, Jesus is right: only "model parameters" (the ones in the Parameters node) can be used in the construction of the geometry. The reason is that those parameters have always a fixed value each time you solve (or at each step of a sweep). "Variables", instead, can be defined using almost anything: you can have a variable that depends on the solution and that cannot be used to construct the geometry directly. If you need to solve problems such as "find the right dimension so that a certain condition is met", you need to follow Ivar's advice and perform a parametric sweep, or use optimization (if you have the required module). -- Andrea Ferrario Electromagnetics Group COMSOL AB

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