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How to export mesh with material properties to MATLAB?

Posted Jan 12, 2012, 12:58 a.m. EST Interfacing Version 4.0, Version 4.0a, Version 4.1, Version 4.2 2 Replies

Zach
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Hello all, I am trying to export my mesh to MATLAB.

With "mphmeshstats" or "mphxmeshinfo", I can only get the vertex of each node in the mesh, and the nodes in each element. But I can't relate the material properties to each element in the mesh.

Does anybody know how to relate material properties to each element in the mesh?

Thanks a lot!

Best,
Kan
2 Replies Last Post Jan 12, 2012, 2:16 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 12, 2012, 1:55 a.m. EST
Hi

I suppose that is because in COMSOL the mesh as the physics are related to the geometry Entities, , but in-between the mesh and the physics you still have the shape functions, so you do not have the direct link physics <-> mesh

Probably you need to do some mapping, coming from "classical FEM" it took me some time to understand, and accept, this difference, it's a cleaner math <-> physics separation than the old way, but when you want to exchange data with other programmes it makes life tougher. Since then I have given up trying to work with classical way

--
Good luck
Ivar
Hi I suppose that is because in COMSOL the mesh as the physics are related to the geometry Entities, , but in-between the mesh and the physics you still have the shape functions, so you do not have the direct link physics mesh Probably you need to do some mapping, coming from "classical FEM" it took me some time to understand, and accept, this difference, it's a cleaner math physics separation than the old way, but when you want to exchange data with other programmes it makes life tougher. Since then I have given up trying to work with classical way -- Good luck Ivar
Zach
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Posted: 1 decade ago Jan 12, 2012, 2:16 a.m. EST
Thank you Ivar!

What do you mean by "in-between the mesh and the physics you still have the shape functions"? I don't get it. I need to know the material related to each element. I don't understand why you involved shape function. The material property (e.g. thermal conductivity) relates to the assembly process, specifically speaking, element-level local stiffness matrix. You time the thermal conductivity with the derivatives of shape function and do the integral. Right?

After digging the COMSOL Java API, I found that I can use

[stats,data]=mphmeshstats(model, 'mesh1');
entity=data.elementity{2}; % elementity{2} is triangular element

Then "entity" contains the "Domain" each element belongs to.

Then I can relate material properties to each domain by using information from
model.material.selection.dom

Problem solved anyway, maybe in a stupid way.

Thanks again.

Best,
Kan
Thank you Ivar! What do you mean by "in-between the mesh and the physics you still have the shape functions"? I don't get it. I need to know the material related to each element. I don't understand why you involved shape function. The material property (e.g. thermal conductivity) relates to the assembly process, specifically speaking, element-level local stiffness matrix. You time the thermal conductivity with the derivatives of shape function and do the integral. Right? After digging the COMSOL Java API, I found that I can use [stats,data]=mphmeshstats(model, 'mesh1'); entity=data.elementity{2}; % elementity{2} is triangular element Then "entity" contains the "Domain" each element belongs to. Then I can relate material properties to each domain by using information from model.material.selection.dom Problem solved anyway, maybe in a stupid way. Thanks again. Best, Kan

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