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Multiple errors

Posted 15 nov 2010, 16:01 GMT-5 3 Replies

Malcolm Macdonald
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I have built a 2D model in Comsol which runs with several modes of physics added to it. However, if I add a simple rectangle to this model I get the error:

Failed to evaluate Jacobian matrix

I have also tried adding a void instead, however the error in this case is:

Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.ec.normJ@VDN$mod1.Vy
- Defined as: (((conj(mod1.ec.Jy)*(((-mod1.ec.sigmayy))))+(conj(mod1.ec.Jy)*(((-mod1.ec.sigmayy)))))*(0.5*(((realdot(mod1.ec.Jy,mod1.ec.Jy)+realdot(mod1.ec.Jx,mod1.ec.Jx))+realdot(mod1.ec.Jz,mod1.ec.Jz))^-0.5)))
Failed to evaluate expression.
- Expression: d(mod1.ec.normJ,mod1.Vy)


I can't figure out what is the cause of the errors when all that is altered is the geometry. The boundary conditions in both these cases are taken care of in the similar way to the original working model.

Thanks for any help...
3 Replies Last Post 16 nov 2010, 15:08 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 16 nov 2010, 01:28 GMT-5
Hi

multiphysics models can become tricky, particularly with many physics. Mostly, when you add a geomtry object / entity to an exisiting model you must recheck all your entitiy selections, oftn this is due to a topological chane of your analysed geometry, and COMSOl cannot always tell right how to reorder and renumber the entities
--
Good luck
Ivar
Hi multiphysics models can become tricky, particularly with many physics. Mostly, when you add a geomtry object / entity to an exisiting model you must recheck all your entitiy selections, oftn this is due to a topological chane of your analysed geometry, and COMSOl cannot always tell right how to reorder and renumber the entities -- Good luck Ivar
Malcolm Macdonald
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Posted: 1 decade ago 16 nov 2010, 11:27 GMT-5
Are you suggesting that the numbering of entities would no longer apply to the physics and boundary conditions originally applied to them? If so, I have rechecked the numbering of the entities to make sure they are defined the way I expect them to be.

Would it make any difference if when I add the rectangle I was previously talking about I add it with a separate physics?
Are you suggesting that the numbering of entities would no longer apply to the physics and boundary conditions originally applied to them? If so, I have rechecked the numbering of the entities to make sure they are defined the way I expect them to be. Would it make any difference if when I add the rectangle I was previously talking about I add it with a separate physics?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 16 nov 2010, 15:08 GMT-5
Hi

it all depends where you add the new rectangle, if it's separate or adjacent to another shape then COMSOL would probably understand and renumber / reorder all entities logically for us.
But if your retange intersects, or changes the topology (i.e. closing an open surface ...) then there are chances that this change will reorder so many domains, boundaries edges and points that COMSOL might well loose "understanding" of what is going on, and your entity selections might become wrong or items might drop out. Analysed geometrical Objects = Entitites are unique and ordered in a logical way, but not necesserely in our logical way

--
Good luck
Ivar
Hi it all depends where you add the new rectangle, if it's separate or adjacent to another shape then COMSOL would probably understand and renumber / reorder all entities logically for us. But if your retange intersects, or changes the topology (i.e. closing an open surface ...) then there are chances that this change will reorder so many domains, boundaries edges and points that COMSOL might well loose "understanding" of what is going on, and your entity selections might become wrong or items might drop out. Analysed geometrical Objects = Entitites are unique and ordered in a logical way, but not necesserely in our logical way -- Good luck Ivar

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