Meshing a model with two separate parts

[Mohammadali Alidoost]

Dear Simvascular Developers,

I have been using a geometry including 2 separate cylinders. When I import them one by one, there is no problem and I can mesh them; therefore, I have two mesh files. However, when I import just one model containing both cylinders (to have just one mesh file), I cannot create a mesh!
I was wondering if you could tell me whether it is possible in Simvascular to mesh a model including 2 separate parts.

Best,
Mohammad

[David Parker]

Hi Mohammad,

I believe the mesh generator assumes a model with a single connected closed surface. Do you get an error message when you try to mesh the model containing two cylinders?

Cheers,
Dave

[Mohammadali Alidoost]

Dear Dave,

Thanks for your response.
Actually, when I imported the cylinders one by one using "Global Max Edge Size" of 0.1, I could mesh them separately (the quality is not important for me in this step).
For the model containing two cylinders, I have tried many "Global Max Edge Sizes" including 0.1, 0.01 and I got this error: "Failed in generating Mesh"!
Moreover, when I use a finer "Global Max Edge Size", say 0.001, my laptop runs out of memory. Therefore, I do not know whether it is the problem of the software package or I can mesh the geometry with a more powerful computer.

Best,
Mohammad

[David Parker]

Hi Mohammad,

I created a model of two cylinders using polydata. When I try to mesh it I get an error from the mesher stating that it can't mesh a model with two regions (i.e. disjoint geometry).

How are you creating the cylinders? Are you importing them?

Cheers,
Dave

[Mohammadali Alidoost]

Hi Dave,

Thanks again!
First, I drew the geometry in CATIA. Then, I am importing the STL file format.

Best,
Mohammad

[David Parker]

Hi Mohammad,

Could you post the STL files here so I can have a look?

Thanks,
Dave

[Mohammadali Alidoost]

Hi Dave,

I have attached the geometry below.

Best,
Mohammad

Two Cylinders-One Part.rar

(41.48 KiB) Downloaded 57 times

[David Parker]

Hi Mohammad,

Thanks for the STL file, just want to understand if there is a problem with SimVascular or if there is a limitation in the TetGen meshing software we integrate into SimVascular.

When trying to mesh the two cylinders I get an error just like you did, and see 'There are too many regions here!' in the SimVascular output, this is coming from the SimVascular code. I disabled this check and was able to mesh the two cylinders but the mesh was really poor, very long tetrahedra. When I meshed a single cylinder from the STL I get the same poor mesh so I think there is a problem meshing STL files. I will find out if that is a known limitation with our mesher.

Cheers,
Dave

[David Parker]

Hi Mohammad,

I did some further tests with the meshing and there is no problem meshing STL files in general, it was that the STL file you provided had a very high resolution so the the mesher created very fine small tetrahedra for it.

I am going to add a check box to the SimVascular Meshing Tool GUI to allow models with multiple regions. A new SimVascular installer will be available around mid-week next week with this functionality.

Cheers,
Dave

[Mohammadali Alidoost]

Hi Dave,

Thanks a lot for taking the time to solve this issue!

Best,
Mohammad