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global equations

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There's a comsol model with 1 module with unknown u and there's another unknown v satisfying an equation f(u,v,a,b,c,d,...)=0, where u is the unknown solved by the module itself, f is defined in 'global expressions' and a~d... are parameters defined in 'global expressions'. In the 'global equations' interface, I set 'name' as v, 'equation' as f and 'initial' as v0. When solving it, an error message says: failed to evaluate u. What's wrong?


2 Replies Last Post 14 sept. 2021, 23:12 UTC−4
Jeff Hiller COMSOL Employee

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Posted: 3 years ago 13 sept. 2021, 10:39 UTC−4
Updated: 3 years ago 13 sept. 2021, 13:33 UTC−4

Hello Carl,

You seem to have the same question as in this older thread and the same solution that Magnus provided in that thread should work for you as well. The short answer is that a Global Equation cannot contain terms that are spatially-dependent.

Best,

Jeff

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Jeff Hiller
Hello Carl, You seem to have the same question as in [this older thread](https://www.comsol.com/forum/thread/18590/a-gloabl-equation-problem?last=2011-05-23T20:35:26Z) and the same solution that Magnus provided in that thread should work for you as well. The short answer is that a Global Equation cannot contain terms that are spatially-dependent. Best, Jeff

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Posted: 3 years ago 14 sept. 2021, 23:12 UTC−4

Thank you very much Jeff!

Thank you very much Jeff!

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