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What's the meaning of this error?

Posted Jan 14, 2011, 12:23 p.m. EST Studies & Solvers Version 4.2 4 Replies

Xiaoyi Yu
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Error

Failed to evaluate variable Jacobian.
- Variable: phi
- Geometry: 1
- Domain: 1

ps: phi is the dependent variable.

Thank you!
4 Replies Last Post May 4, 2012, 7:30 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 14, 2011, 2:54 p.m. EST
Hi

THe jacobian is build up of the derivatives of the dependent variables, here phi, so something is not well enough defined to allow COMSOL to elaborate the derivatives of phy. Perhaps some contradiction in a BC, or a step function with two derivatives, of different values for the same (probably starting point).

--
Good luck
Ivar
Hi THe jacobian is build up of the derivatives of the dependent variables, here phi, so something is not well enough defined to allow COMSOL to elaborate the derivatives of phy. Perhaps some contradiction in a BC, or a step function with two derivatives, of different values for the same (probably starting point). -- Good luck Ivar
Malavika Prasanna
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Posted: 1 decade ago May 3, 2012, 11:06 a.m. EDT
Hello Evar,
I am building a model of "capacitive accelerometer". And i got this error.
Moreover, i am not able to find out the dependent variable mod1.u!

Failed to evaluate variable Jacobian.
- Variable: mod1.u
- Geometry: 1
- Boundary: 1 2 3 4 9 11 112 113 114 164 204 206

Can you please help with this?

Thank you
Hello Evar, I am building a model of "capacitive accelerometer". And i got this error. Moreover, i am not able to find out the dependent variable mod1.u! Failed to evaluate variable Jacobian. - Variable: mod1.u - Geometry: 1 - Boundary: 1 2 3 4 9 11 112 113 114 164 204 206 Can you please help with this? Thank you
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 3, 2012, 2:49 p.m. EDT
Hi

it's simply "u", the variable name.
The Jacobian error, most often comes from an initial value or a BC that is defined such that the derivative of u is undefined, The solver uses the estimated derivatives to choose the next solving step, but if you use bolean equations or values that become undefined in the BC definitions then COMSOL might not manage to estimate any derivatives, and then the solver fails.

--
Good luck
Ivar
Hi it's simply "u", the variable name. The Jacobian error, most often comes from an initial value or a BC that is defined such that the derivative of u is undefined, The solver uses the estimated derivatives to choose the next solving step, but if you use bolean equations or values that become undefined in the BC definitions then COMSOL might not manage to estimate any derivatives, and then the solver fails. -- Good luck Ivar
Malavika Prasanna
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Posted: 1 decade ago May 4, 2012, 7:30 a.m. EDT
HI,
I did try changing the boundary and initial conditions. I have attached the model with this message. Can you please check the error in this and let me know how i should proceed?


Thank you

Malavika
HI, I did try changing the boundary and initial conditions. I have attached the model with this message. Can you please check the error in this and let me know how i should proceed? Thank you Malavika

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