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Hello Sang Ha Shin

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Have you figured out how to use the mesh part?

Hi,
I am also having the same problem , except that my solid geometry was buit in comsol and I am unable to jon the two. HAve you found the solution to your problem. It would be a great help to me as well.
Thanks

Hi

I do not believe you can "join" an external mesh and a geometry. As COMSOL generates the mesh based on the geometry, and in that order. So why not mesh in COMSOL ?

For simple mesh shapes, if you have them in NASTRAN neutral file format, and you have v3.5 you might import it, and tempt a "create geometry from mesh" This will generate a COMSOL geometry onto which you can then apply your physics and BC, and then remesh (if required) and solve.

Another point: STL file format is no true 3D, its 2D or at most 2.5D and has some of the same issues as the regeneration of a "geometry" from it as you have with a mesh. Parasolid, step or other "higher order" 3D kernels formats are far better.

The points above is a major difference between COMSOL and "older" FEM programmes, and so long this is not correctly understood and accepted you will end up loosing your time and getting frustrated (as I did in the beginning) . But, once accepted you find new ways to do things and you will, I'm sure, find this approach far more powerful

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Good luck
Ivar

Hi Ivar,
Thank you very much for this information as it will greatly help me.
The mesh has been generated in simpleware of a MRI object wichh i need to do heat analysis using comsol with necessary geometry to assist the simulation to be buit in comsol.
I have read some of your discussions in the forum, I just wanted to ask is it possible for me to import mesh in geometry1 and design the compononent in geometry 2 of the same file and use the move operation to assemble the two geometries for me to carry out the simulation.
The other option that I could think of was to convert the mesh into a geometry but I was constantly given .
an error message while doing so : error 2211: face cannot be parametrized : face 1
Is there any other way to assemble the imported mesh of mri object and assemble it to system in comsol.
Please guide. Thanks again your information is very useful to me.
Isshaa

Hi

If it's a free "meshed" geometry (i.e. of MRI type) then there are some third party vendors that have the appropriate software to translate that, see the main web page of COMSOL. Certainly there must be some free-ware too but I do not know about that.

I do not believe its possible to join them as such, or then with some heavy Matlab fiddling perhaps (I gave up importing even ANSYS codes, would have been nice too).

As I said I had some success with COMSOL 3.5a and the command "create analysed geometry from mesh", but that implies loading in the mesh in NASTRAN Neutral file format. For some of my models it managed to regroup the lower level mesh to generate higher order objects, but not always. I'm not sure this feature is present in v4 even

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Good luck
Ivar

Hi,

In version 4.1 you can base a geometry on an imported NASTRAN or STL file for 3D models. Right-click the Mesh node and select Import to import a mesh.

It is not possible to combine solid modeling with a geometry based on a mesh in the same model, but you might be able to use two models (one mesh-based geometry and one based on solid geometry modeling) and connect the two using a coupling operator.

Best regards,
Magnus Ringh, COMSOL

HI Ivar,
Thanks for the help, I have managed to join the two assemblies as sugested by you by importing my mri object as a geometry , but when I have to mesh the two assemblies together I receive an error 2100: internal error in geometry decomposition, or sometimes error 4100, failure to generate mesh for subdomain: subdomain 1 internal error in boundary respecting
what would that mean, do i have to repair the imported mesh .
also when i try to mesh the two assemblies when they are not joined together, in the same geometry, i receive error
2052: faces are two close in 3D domain.
What exactly accounts as face in comsol and how can I control them if they are designed separately in two softwares.
Please guide .
Thanking You, and sorry for the trouble.
Isshaa

HI Magnus R,
Many Thanks for the information great help, but I am using 3.4 version so I mangaged to import the mri model as geometry, with suggestion of Ivar, (it was useful) but is now finding difficult to mesh this geometry with the comsol geometry design, receiving errors pertaing to sub-domains, faces and small dimension, will have to find a way through this as I cannot control the mri object dimensions always .
Also I believe you are a COmsol employee, on comsol website there is a news article, stating comsol and simpleware partnership for being able to export MRI objects to comsol so that they can be meshed and be simulated in comsol, I have done this defintely works but only if the MRI object is a mesh imported to comsol, if imported as geometry I get above mentioned details. I just wanted to know if there is any pdf resource to this importing of mri meshes to comsol, I wonder if this can guide me as well.
Thanks a lot for your help, will defintely keep this in mind for further analysis.
Isshaa

Hi Magnus,
It seems to work the way you have mentioned, I have been able to join my two geometeries (one is mesh based geometry from an stl file ) using merge component option. The thing is when i merge the two geometries i can select the physics condition to merge with either of the geometeries, but it does not allow me to merge more than one physics condition, and when simulated is not considering the physic condition for the secong geometry.
You had mentioned about coupling operators ; i saw through it and it seems that the coupling operators also need expression to be set, but i am not able to understand how a coupling operator actually operates as in what is it flow direction, because my geometries are dependent on the same variables temperature ; i cannot seem to connect them together.
Also can I connect two geometries by creating identity pairs.
Please guide it will be of great help.
Thanks and take care.