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Failed to evaluate variable Jacobian

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Hi,

I am running a coupled problem, where I am using the Physics Transport of Diluted Species, Heat Transfer as well as general PDEs.

I got an error message saying

Failed to evaluate variable Jacobian
- Variable: mod1.c
- Global scope

where c is the dependent variable for the transport module.

Following some posts here on this error message, I have checked all the variable definitions several times and made sure that they are not simple, like a, b...

Could anyone please give me some clue as what things I should look for for this kind of error?


Your response is much appreciated.


2 Replies Last Post 27.04.2011, 10:27 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 26.04.2011, 16:20 GMT-4
Hi

COMSOL uses the Jacobian of all dependent variables to help the solver iterate.

So if you define your "c" in such a way that it might not be derivable at least once (i.e. but not only: step function, discontinuities ...) then you might get this error message, hope it helps ;)

--
Good luck
Ivar
Hi COMSOL uses the Jacobian of all dependent variables to help the solver iterate. So if you define your "c" in such a way that it might not be derivable at least once (i.e. but not only: step function, discontinuities ...) then you might get this error message, hope it helps ;) -- Good luck Ivar

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Posted: 1 decade ago 27.04.2011, 10:27 GMT-4
Hi Ivar,

Thank you very much for the reply.

The c is the concentration, which is the dependent variable of the transport module. I don't seem to have something that is discontinuous....

This is like debugging and so frustrating.. hehe.
Hi Ivar, Thank you very much for the reply. The c is the concentration, which is the dependent variable of the transport module. I don't seem to have something that is discontinuous.... This is like debugging and so frustrating.. hehe.

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