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Is it possible to choose curl element for two dependent variables for a 2D model?
Posted 15 sept. 2012, 17:02 UTC−4 Version 4.2a 1 Reply
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Hi, all
For the question, if the model only has two dependent variables it seems possible. What if the model has 3 or more dependent variables?
Thanks!
For the question, if the model only has two dependent variables it seems possible. What if the model has 3 or more dependent variables?
Thanks!
1 Reply Last Post 25 sept. 2012, 04:57 UTC−4
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Posted:
1 decade ago
Hello,
In the PDE interfaces, the curl (and also div-) elements are only available when the number of dependent variables is the same as the space dimension. The reason is that, conceptually, each PDE interface works with one physical quantity (you cannot set different units for different dependent variables). Normally, this imposes no limitations, but there are cases where you may need to model also the out-of-plane component of a vector. I guess your case is something like that.
There are two possible work-arounds: either you can split your equations into more than one PDE interfaces, such that you can select curl elements for two of the components; or you can add a weak contribution (from More on the interface context menu) and then an auxiliary variable as a subfeature to the weak contribution. The latter may be the best option if your problem is indeed about an out-of-plane component of a vector.
best regards
Nils Malm
COMSOL AB
In the PDE interfaces, the curl (and also div-) elements are only available when the number of dependent variables is the same as the space dimension. The reason is that, conceptually, each PDE interface works with one physical quantity (you cannot set different units for different dependent variables). Normally, this imposes no limitations, but there are cases where you may need to model also the out-of-plane component of a vector. I guess your case is something like that.
There are two possible work-arounds: either you can split your equations into more than one PDE interfaces, such that you can select curl elements for two of the components; or you can add a weak contribution (from More on the interface context menu) and then an auxiliary variable as a subfeature to the weak contribution. The latter may be the best option if your problem is indeed about an out-of-plane component of a vector.
best regards
Nils Malm
COMSOL AB