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export mesh data for an explicit selection
Posted 15 mag 2013, 11:01 GMT-4 Mesh, Parameters, Variables, & Functions, Results & Visualization 3 Replies
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Dear all,
I am a relatively new user COMSOL with a lot of Finite Element experience both on the programming and theory level. I started with COMSOL today which went actually quite fine and fast.
I would like to use that to interface assemled system matrices and mesh data to my own solvers. And it was successful for simple shell models.
At this point, I am also wondering if that is possible to export some selected node data or not. What I am directly interested is 'can I create node groups in COMSOL' which can be exported in some kind of text data file format or in binary file format?
Let me be more specific, lets say I have two fixed edges of a square plate and I would like know which nodes are associated with this selected fixed edges so that I can extract the constrained dof infornation myself. These kinds of information might give me more freedom for simple FRF analysis that I would like to conduct.
I learned that I can extract the matrices Kc and K, for instance, for the system stiffness matrix which represent the matrix on which the boundary conditions are applied and the full system matrix without any boundary conditions applied, respectively.
I would like to know or compute the fixed dof information by either getting it from COMSOL(which would be nice since no extra computations will be necessary.) or by iterating over the nodes myself.
Any ideas or pointers are appreciated on this matter.
Best regards,
Umut
I am a relatively new user COMSOL with a lot of Finite Element experience both on the programming and theory level. I started with COMSOL today which went actually quite fine and fast.
I would like to use that to interface assemled system matrices and mesh data to my own solvers. And it was successful for simple shell models.
At this point, I am also wondering if that is possible to export some selected node data or not. What I am directly interested is 'can I create node groups in COMSOL' which can be exported in some kind of text data file format or in binary file format?
Let me be more specific, lets say I have two fixed edges of a square plate and I would like know which nodes are associated with this selected fixed edges so that I can extract the constrained dof infornation myself. These kinds of information might give me more freedom for simple FRF analysis that I would like to conduct.
I learned that I can extract the matrices Kc and K, for instance, for the system stiffness matrix which represent the matrix on which the boundary conditions are applied and the full system matrix without any boundary conditions applied, respectively.
I would like to know or compute the fixed dof information by either getting it from COMSOL(which would be nice since no extra computations will be necessary.) or by iterating over the nodes myself.
Any ideas or pointers are appreciated on this matter.
Best regards,
Umut
3 Replies Last Post 16 mag 2013, 10:01 GMT-4
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Posted:
1 decade ago
Dear Umut,
have you taken a look at the chapter in the LiveLink to MATLAB users guide on "Retrieving Xmesh Information"?
In the 4.3a version this is on page 159.
Best regards,
Frank
have you taken a look at the chapter in the LiveLink to MATLAB users guide on "Retrieving Xmesh Information"?
In the 4.3a version this is on page 159.
Best regards,
Frank
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Posted:
1 decade ago
Hi Frank,
Indeed, I am looking into that section.
From
info.elements.edg.nodes
I can get the list of nodes on the edges of a simple plate, where info is the structure returned from
info = mphxmeshinfo(model);
However, this is still not a direct answer to my question. What I am after is to really create a selection group under Definitions node(I guess this is called as an Explicit selection) and retrieve the node list associated to this selection. Later on, this selection groups can be extended to include certain surfaces of finite element model. However, there is a subtle difference here. Namely, when a finite element mesh is created, the geometry information is lost but I was guessing the kernel of COMSOL still knows which FE information is associated to which geometrical entities. Or somehow should keep pointers to this information internally.
The question is that is this information transparent to the user or not?
Best,
Umut
Indeed, I am looking into that section.
From
info.elements.edg.nodes
I can get the list of nodes on the edges of a simple plate, where info is the structure returned from
info = mphxmeshinfo(model);
However, this is still not a direct answer to my question. What I am after is to really create a selection group under Definitions node(I guess this is called as an Explicit selection) and retrieve the node list associated to this selection. Later on, this selection groups can be extended to include certain surfaces of finite element model. However, there is a subtle difference here. Namely, when a finite element mesh is created, the geometry information is lost but I was guessing the kernel of COMSOL still knows which FE information is associated to which geometrical entities. Or somehow should keep pointers to this information internally.
The question is that is this information transparent to the user or not?
Best,
Umut
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Posted:
1 decade ago
Dear Umut,
You can either use explicit, ball, or box selections. Explicit selections can be created automatically by enabling the "Create selections" check-box for the geometric entity. model.selection(<tag>).entities(dim); can then be used to obtain the geometric entity indices included in the selection.
When selections are defined, mphmeshstats can be used to obtain data on the nodes associated with these.
Best regards,
Reine Granström
What I am after is to really create a selection group under Definitions node(I guess this is called as an Explicit selection) and retrieve the node list associated to this selection. Later on, this selection groups can be extended to include certain surfaces of finite element model.
You can either use explicit, ball, or box selections. Explicit selections can be created automatically by enabling the "Create selections" check-box for the geometric entity. model.selection(<tag>).entities(dim); can then be used to obtain the geometric entity indices included in the selection.
However, there is a subtle difference here. Namely, when a finite element mesh is created, the geometry information is lost but I was guessing the kernel of COMSOL still knows which FE information is associated to which geometrical entities. Or somehow should keep pointers to this information internally.
The question is that is this information transparent to the user or not?
When selections are defined, mphmeshstats can be used to obtain data on the nodes associated with these.
Best regards,
Reine Granström