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3D meshing

Posted Aug 29, 2011, 11:00 a.m. EDT Geometry, Mesh, Results & Visualization Version 4.0 4 Replies

LiWah Wong
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Hi people

I have a 3D model like the attachment.
As for all the fractures and faults inside (in the centre of) the block, I did a triangular meshing and as for the block itself, I did a tetrahedral mesh.
I received the following error message upon a run:



Failed to find consistent initial values.
Singular matrix

There are 9642 void equations (empty rows in matrix) for the variable mod1.p
and similarly for the degrees of freedom (empty columns in matrix)



I wonder if it has something to do with the 3D meshing, as if the mesh is not spreading all over the block inself from outside to inside?

Appreciate your help!!


regards
Liwah

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4 Replies Last Post Aug 30, 2011, 11:27 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 Aug 30, 2011, 3:20 a.m. EDT
Hi

Well from a first view on could believe that your mesh is only a boundary mesh without any volume elements, or that your geometry is such that the domains and boundaries are not well defines. Perhaps go through the domains, one by one (Selection List) and then the same for the boundaries. Check also the mesh statistics

If the mesh seems OK, it's related to a poor definition of the boundary conditions, something must be missing

--
Good luck
Ivar
Hi Well from a first view on could believe that your mesh is only a boundary mesh without any volume elements, or that your geometry is such that the domains and boundaries are not well defines. Perhaps go through the domains, one by one (Selection List) and then the same for the boundaries. Check also the mesh statistics If the mesh seems OK, it's related to a poor definition of the boundary conditions, something must be missing -- Good luck Ivar
LiWah Wong
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Posted: 1 decade ago Aug 30, 2011, 7:10 a.m. EDT
Hi

many thanks for your inputs :) may I know where i.e user interface to define volume elements? I found 'volume of elements and mesh' in help search but I have no ideas where in 'model builder' should I work on that?

many thanks again for your time and great help!

regards
Liwah


Hi

Well from a first view on could believe that your mesh is only a boundary mesh without any volume elements, or that your geometry is such that the domains and boundaries are not well defines. Perhaps go through the domains, one by one (Selection List) and then the same for the boundaries. Check also the mesh statistics

If the mesh seems OK, it's related to a poor definition of the boundary conditions, something must be missing

--
Good luck
Ivar


Hi many thanks for your inputs :) may I know where i.e user interface to define volume elements? I found 'volume of elements and mesh' in help search but I have no ideas where in 'model builder' should I work on that? many thanks again for your time and great help! regards Liwah [QUOTE] Hi Well from a first view on could believe that your mesh is only a boundary mesh without any volume elements, or that your geometry is such that the domains and boundaries are not well defines. Perhaps go through the domains, one by one (Selection List) and then the same for the boundaries. Check also the mesh statistics If the mesh seems OK, it's related to a poor definition of the boundary conditions, something must be missing -- Good luck Ivar [/QUOTE]
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Aug 30, 2011, 7:41 a.m. EDT
Hi

if you are in 3D the default is volume "tetrahedral" (onto which you have by default 2nd order shape functions which gives you more or less the equivalent to hex type in older software)

You need to apply manually surface mesh (as seed meshes), but normally a default "remaining" Tetrahedral remains as last node. Mostly I start by using the default mesher, only when it fails then I need to work "manually"

Note v4.0 was rather weak in functionality, update to the latest version you will be less frustrated ;)

--
Good luck
Ivar
Hi if you are in 3D the default is volume "tetrahedral" (onto which you have by default 2nd order shape functions which gives you more or less the equivalent to hex type in older software) You need to apply manually surface mesh (as seed meshes), but normally a default "remaining" Tetrahedral remains as last node. Mostly I start by using the default mesher, only when it fails then I need to work "manually" Note v4.0 was rather weak in functionality, update to the latest version you will be less frustrated ;) -- Good luck Ivar
LiWah Wong
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Posted: 1 decade ago Aug 30, 2011, 11:27 a.m. EDT
Hi

you are right, v4.0 is kinda driving me crazy.
But anyway, I am still trying my luck with the mesh, I still cant do the volumetric mesh, as if there aint a way to do it... I tried swept, scale and distribution, to no avail... :(

regards
Liwah
Hi you are right, v4.0 is kinda driving me crazy. But anyway, I am still trying my luck with the mesh, I still cant do the volumetric mesh, as if there aint a way to do it... I tried swept, scale and distribution, to no avail... :( regards Liwah

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