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Coupling of PDES

Posted 1 apr 2019, 06:31 GMT-4 Equation-Based Modeling Version 5.3a 3 Replies

Adamu Ibrahim
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I'm looking to solve a series of PDEs in COMSOL, but I'm not sure how to couple the four of them. There are four dependent variables. How do I couple them together so that I can use dependent variables from one physics in another physics?

3 Replies Last Post 1 apr 2019, 10:53 GMT-4
Jeff Hiller COMSOL Employee

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Posted: 5 years ago 1 apr 2019, 09:19 GMT-4

Hello Adamu,

If you use two (or more) dependent variables in one PDE, they will be coupled. There's nothing to it, really; just use the name of one (or more) of your unknowns in the equation for another of the unknowns. Or coupling can happen due to boundary conditions, edge conditions, constraints, but in all cases things work the same way: just type what you would write on paper.

If you're not doing that already, you'll want to use a single physics interface for all 4 dependent variables, rather than 4 physics interfaces one for each dependent variables.

Best,

Jeff

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Jeff Hiller
Hello Adamu, If you use two (or more) dependent variables in one PDE, they will be coupled. There's nothing to it, really; just use the name of one (or more) of your unknowns in the equation for another of the unknowns. Or coupling can happen due to boundary conditions, edge conditions, constraints, but in all cases things work the same way: just type what you would write on paper. If you're not doing that already, you'll want to use a single physics interface for all 4 dependent variables, rather than 4 physics interfaces one for each dependent variables. Best, Jeff
Adamu Ibrahim
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Posted: 5 years ago 1 apr 2019, 10:15 GMT-4

Hi Jeff,

I am trying to model 4 equations. However, when I input the variable u1 in the first equation, and when I try to input same varaible as u1 in the second equation it gives me an error message. I have attached here my sample equations

Hi Jeff, I am trying to model 4 equations. However, when I input the variable u1 in the first equation, and when I try to input same varaible as u1 in the second equation it gives me an error message. I have attached here my sample equations

Attachments:

Jeff Hiller COMSOL Employee

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Posted: 5 years ago 1 apr 2019, 10:53 GMT-4
Updated: 5 years ago 1 apr 2019, 11:20 GMT-4

Hi Adamu,

It would be difficult to say anything intelligent without seeing your mph file. Please post it here, thanks.

Jeff

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Jeff Hiller
Hi Adamu, It would be difficult to say anything intelligent without seeing your mph file. Please post it here, thanks. Jeff

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