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How to link Two physics in Comsol

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I am solving a problem using Two physics Shell, Shell 2 (I applied shell to particular region, Shell 2 to remaining) , Comsol Solver is Solving Two physics separately and it is showing results separately for two physics that means it is splitting the model, Can anyone tell me how to link those two physics such that entire body will be solved as single
Thanking You

1 Reply Last Post 03.07.2014, 11:02 GMT-4
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago 03.07.2014, 11:02 GMT-4
Hi,

The first thing you should consider is why you need to use two separate physics interfaces? It is rather uncommon that there is really a need for two physics interfaces of the same kind in a model.

Connecting two physics interfaces of the same type is usually easy, though. You just rename the degrees of freedom (under Shell -> Dependent variables) so that they are the same for both physics interfaces.

For the special case of shells, this not the whole truth, though. Coupling shells can in certain cases be rather complicated. If you for example would model a T or L junction using two different physics interfaces, both of them would see themselves as perfectly flat at the connecting line. This would (after joining the degrees of freedom) create a severe overconstraint, since two out of three rotational degrees of freedom would be automatically constrained (rotation about both normals). At such a junction line, all rotational degrees of freedom should actually be active. Handling this condition is out of scope for this answer, but please be warned.

You would still have to add duplicate plots (e.g. one for shell.mises and one for shell2.mises). If you choose to use separate physics interfaces, then each of them contains its own variables. Both plots can be in the same plot group though, so it will look as one plot if you are careful with the settings.

Regards,
Henrik
Hi, The first thing you should consider is why you need to use two separate physics interfaces? It is rather uncommon that there is really a need for two physics interfaces of the same kind in a model. Connecting two physics interfaces of the same type is usually easy, though. You just rename the degrees of freedom (under Shell -> Dependent variables) so that they are the same for both physics interfaces. For the special case of shells, this not the whole truth, though. Coupling shells can in certain cases be rather complicated. If you for example would model a T or L junction using two different physics interfaces, both of them would see themselves as perfectly flat at the connecting line. This would (after joining the degrees of freedom) create a severe overconstraint, since two out of three rotational degrees of freedom would be automatically constrained (rotation about both normals). At such a junction line, all rotational degrees of freedom should actually be active. Handling this condition is out of scope for this answer, but please be warned. You would still have to add duplicate plots (e.g. one for shell.mises and one for shell2.mises). If you choose to use separate physics interfaces, then each of them contains its own variables. Both plots can be in the same plot group though, so it will look as one plot if you are careful with the settings. Regards, Henrik

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