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Where is the error of my model ? (model file has been attached)

Posted 20.02.2011, 14:58 GMT-5 Version 4.0 5 Replies

Xiaoyi Yu
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Only the PDE physic was used, the error notice were as follows, details about the model (V4.0) please see the attachment. Thank you!

ERROR:
Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
There are 50188 equations giving NaN/Inf in the matrix rows for the variable mod1.theta
at coordinates: (-0.005,-0.005), (-0.005,-0.00495), (-0.005,-0.0049), (-0.00496745,-0.0049161), (-0.0049349,-0.0049322), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns

Attachments:

5 Replies Last Post 21.02.2011, 17:20 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20.02.2011, 16:33 GMT-5
Hi

My understanding is that such errors occure if you have not defined enough (or fully independent) boundary conditions, COMSOL accepts only a coherehnt set such to receive a single solution. It is not set-up to handle muliple simultaneous solutions of the PDE

--
Good luck
Ivar
Hi My understanding is that such errors occure if you have not defined enough (or fully independent) boundary conditions, COMSOL accepts only a coherehnt set such to receive a single solution. It is not set-up to handle muliple simultaneous solutions of the PDE -- Good luck Ivar
Xiaoyi Yu
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Posted: 1 decade ago 20.02.2011, 20:05 GMT-5

Hi

My understanding is that such errors occure if you have not defined enough (or fully independent) boundary conditions, COMSOL accepts only a coherehnt set such to receive a single solution. It is not set-up to handle muliple simultaneous solutions of the PDE

--
Good luck
Ivar


Thank you, Ivar! You mean, there are two equations in a PDE physic but only one set of boundary conditions? So, I added another physics, Heat transfer (ht), because the second equation is heat transfer equation with heat source term. But same errors still occurred.
[QUOTE] Hi My understanding is that such errors occure if you have not defined enough (or fully independent) boundary conditions, COMSOL accepts only a coherehnt set such to receive a single solution. It is not set-up to handle muliple simultaneous solutions of the PDE -- Good luck Ivar [/QUOTE] Thank you, Ivar! You mean, there are two equations in a PDE physic but only one set of boundary conditions? So, I added another physics, Heat transfer (ht), because the second equation is heat transfer equation with heat source term. But same errors still occurred.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21.02.2011, 01:30 GMT-5
Hi

adding physics is one thing, but you need to give sufficient restrictive boundary conditions else there are many (infinite) number of solutions and your matrices are not fully populated. That is my understanding of your error message.

Check if you do not need to add some further limitations on the boundaries

You should get hands on the book of Zimmermann (its for 3.3 but fully adaptable to 4) see the main web site book references

--
Good luck
Ivar
Hi adding physics is one thing, but you need to give sufficient restrictive boundary conditions else there are many (infinite) number of solutions and your matrices are not fully populated. That is my understanding of your error message. Check if you do not need to add some further limitations on the boundaries You should get hands on the book of Zimmermann (its for 3.3 but fully adaptable to 4) see the main web site book references -- Good luck Ivar
Xiaoyi Yu
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Posted: 1 decade ago 21.02.2011, 08:50 GMT-5

Hi

adding physics is one thing, but you need to give sufficient restrictive boundary conditions else there are many (infinite) number of solutions and your matrices are not fully populated. That is my understanding of your error message.

Check if you do not need to add some further limitations on the boundaries

You should get hands on the book of Zimmermann (its for 3.3 but fully adaptable to 4) see the main web site book references

--
Good luck
Ivar


Thank you, Ivar. Do you refer to this book:
Multiphysics Modeling With Finite Element Methods (Series on Stability, Vibration and Control of Systems: Series a)
[QUOTE] Hi adding physics is one thing, but you need to give sufficient restrictive boundary conditions else there are many (infinite) number of solutions and your matrices are not fully populated. That is my understanding of your error message. Check if you do not need to add some further limitations on the boundaries You should get hands on the book of Zimmermann (its for 3.3 but fully adaptable to 4) see the main web site book references -- Good luck Ivar [/QUOTE] Thank you, Ivar. Do you refer to this book: Multiphysics Modeling With Finite Element Methods (Series on Stability, Vibration and Control of Systems: Series a)
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21.02.2011, 17:20 GMT-5
Hi

indeed this one, I'm sure they have it in a local library (books are becoming expensive to buy these days). I find it very usefull, unfortunately it's written fr 3.3 but most of the examples are traightforward to implement in v4

www.comsol.eu/support/books/mmwfem/

--
Good luck
Ivar
Hi indeed this one, I'm sure they have it in a local library (books are becoming expensive to buy these days). I find it very usefull, unfortunately it's written fr 3.3 but most of the examples are traightforward to implement in v4 http://www.comsol.eu/support/books/mmwfem/ -- Good luck Ivar

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