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stifness matrix

Posted 27.05.2011, 19:37 GMT-4 Fluid & Heat Version 4.1 3 Replies

Osameh Ghazian
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what does this error mean ?

Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
There are 70744 equations giving NaN/Inf in the matrix rows for the variable mod1.p
at coordinates: (0,0), (0,2.5e-005), (1.63166e-005,1.70061e-005), (2.5e-005,0), (0,5e-005), ...
There are 70744 equations giving NaN/Inf in the matrix rows for the variable mod1.u
at coordinates: (0,0), (0,2.5e-005), (1.63166e-005,1.70061e-005), (2.5e-005,0), (0,5e-005), ...
There are 70744 equations giving NaN/Inf in the matrix rows for the variable mod1.v
at coordinates: (0,0), (0,2.5e-005), (1.63166e-005,1.70061e-005), (2.5e-005,0), (0,5e-005), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns


thanks,
3 Replies Last Post 31.05.2011, 01:22 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30.05.2011, 01:06 GMT-4
Hi

this means that your dependent variables p,u,v ... cannot be solved due to an error in the stiffness matrix, some of the (most probably) material parameters are not defined correctly.
Recheck your "Material" node to see if there are not some "red flags" therein. Or you have set nu>= 0.5 or some equation you are using that is not correctly defined

--
Good luck
Ivar
Hi this means that your dependent variables p,u,v ... cannot be solved due to an error in the stiffness matrix, some of the (most probably) material parameters are not defined correctly. Recheck your "Material" node to see if there are not some "red flags" therein. Or you have set nu>= 0.5 or some equation you are using that is not correctly defined -- Good luck Ivar
Osameh Ghazian
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Posted: 1 decade ago 30.05.2011, 07:48 GMT-4
thanks,

what do u mean by mean nu ??

I want to solve the inviscid flow, so I put dynamic viscosity to zero and activate the streamline diffusion for more convergence, when I use streamline diffusion , i get that error.

best
thanks, what do u mean by mean nu ?? I want to solve the inviscid flow, so I put dynamic viscosity to zero and activate the streamline diffusion for more convergence, when I use streamline diffusion , i get that error. best
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 31.05.2011, 01:22 GMT-4
Hi

sorry I was thinking "solid" and Poisson "nu" which is giving similar effects if someone put nu >= 0.5, but nu=0.495 is OK

but then perhaps its the dynamic viscosity that is playing you a game ;) try 0.001 or something "small"

--
Good luck
Ivar
Hi sorry I was thinking "solid" and Poisson "nu" which is giving similar effects if someone put nu >= 0.5, but nu=0.495 is OK but then perhaps its the dynamic viscosity that is playing you a game ;) try 0.001 or something "small" -- Good luck Ivar

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