Jim Freels
mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted:
1 decade ago
Jan 21, 2011, 5:21 p.m. EST
Your model is probably set up to solve the physics using multigrid solver by default. In simplified terms, the multigrid means that it requires multiple grids, or meshes, to solve the problem. Usually, you start with the most detailed mesh, then work down to a coarse mesh that can be solved using a direct solver. If you use COMSOL automated procedure, then the mesh is automatically generated for you between the fine mesh (assume the one you inputted) to the coarse mesh. This only works for free meshes. So, since you have input a mesh specifically from a 3rd party, I would not expect COMSOL to be able to automatically remesh to a coarse mesh.
I would recommend using the manual mesh generation, and use your 3rd-party program to create consecutive coarse meshes until you get a coarse mesh that can be solved directly, then the multigrid method should work. Multigrid works great, but it is tricky and I recommend you study up on it before trying to use it.
Alternatively, if your computer has enough memory, you can solve the problem using the direct solver. Better yet, solve it on a cluster.
Your model is probably set up to solve the physics using multigrid solver by default. In simplified terms, the multigrid means that it requires multiple grids, or meshes, to solve the problem. Usually, you start with the most detailed mesh, then work down to a coarse mesh that can be solved using a direct solver. If you use COMSOL automated procedure, then the mesh is automatically generated for you between the fine mesh (assume the one you inputted) to the coarse mesh. This only works for free meshes. So, since you have input a mesh specifically from a 3rd party, I would not expect COMSOL to be able to automatically remesh to a coarse mesh.
I would recommend using the manual mesh generation, and use your 3rd-party program to create consecutive coarse meshes until you get a coarse mesh that can be solved directly, then the multigrid method should work. Multigrid works great, but it is tricky and I recommend you study up on it before trying to use it.
Alternatively, if your computer has enough memory, you can solve the problem using the direct solver. Better yet, solve it on a cluster.
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Posted:
1 decade ago
Dec 19, 2012, 4:26 a.m. EST
Hi Zeeshan,
I have the same problem. I want to export a mesh file from Simpleware to COMSOL and appers the problem setting up multigrid. Have you solved the problem?. Could you help me?.
Thanks,
Sergio Gómez
Hi Zeeshan,
I have the same problem. I want to export a mesh file from Simpleware to COMSOL and appers the problem setting up multigrid. Have you solved the problem?. Could you help me?.
Thanks,
Sergio Gómez
Jim Freels
mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted:
1 decade ago
Dec 20, 2012, 10:49 a.m. EST
Please see my recommendation just above your entry in this thread. Set up your meshes manually.
Please see my recommendation just above your entry in this thread. Set up your meshes manually.
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Posted:
1 decade ago
Jan 23, 2013, 7:59 p.m. EST
Hi Sergio,
In addition to recommendations by James,
COMSOL is using the power of Multigrid to make an increasingly finer mesh. However, doing this for imported mesh is not a trivial task for COMSOL. To get rid of this problem you have 3 options:
1. Use direct solver instead of iterative, which does not use the multigrid. You need much more RAM for direct solution.
2. Use iterative solver with multigrid option disabled. To do this go to Study 1/solver configuration/solver 1/Iterative/multigrid
3. If you are using Simpleware you can generate a range of mesh size for the same geometry with +FE Free mesh coarseness slider.
Good luck,
saeid
Hi Sergio,
In addition to recommendations by James,
COMSOL is using the power of Multigrid to make an increasingly finer mesh. However, doing this for imported mesh is not a trivial task for COMSOL. To get rid of this problem you have 3 options:
1. Use direct solver instead of iterative, which does not use the multigrid. You need much more RAM for direct solution.
2. Use iterative solver with multigrid option disabled. To do this go to Study 1/solver configuration/solver 1/Iterative/multigrid
3. If you are using Simpleware you can generate a range of mesh size for the same geometry with +FE Free mesh coarseness slider.
Good luck,
saeid
