Learning Forum

[Valeria Guadagno]

Hi!

I realized a geometry model through segmentation of a biomedical image using 3D slicer. Now I need to mesh it in order to perform a CFD on Ansys Fluent.

However, I met so many problems:

1. My 3D model is in a .stl format and it doesn't allow the mesher to create the mesh since the huge number of facets makes the geometry too complicated. So, on the geometry step I converted the facets into a solid and passed it to the mesher.
2. At this point the mesh was created, but with big elements, which I need to be much smaller. However, by decreasing the elements size I got this error: "Execution error inside the mesher. The process suffered an unhandled exception or ran out of memory".
3. I also need to perform inflation of the mesh. However, one of the input required is the "boundary", that has to be a surface. I could probably create (but I'm not sure) a surface named selection given but the sum of all the small faces that make up my solid's surface, but they are thousands and I have to select them one-by-one, and of course this makes the process too hard. Another option I though about was to create a "patch body", made of the solid surface, from the geometry software, usign the AutoSkin function, so to use it as the surface I need for the "boundary" voice in "inflation" for the mesh. However in this case I would have two separate models in the mesher: a solid model + the surface model, so I don't know if this solution would work.

 

Please since I'm not an expert and I'm trying to figure things out, your help would be really apreciated!

Thank you

[Rob]

Meshing stl's isn't always easy. How are you segmenting the DICOM stack and creating the original stl? 

Fluent Meshing is usually the better tool, but the workflows may not be suitable as you may need to create the surface/mesh objects and use the slightly older approach. 

[Valeria Guadagno]

Yes, I segmented a DICOM file and created an original stl. Do you think it could be successfull to convert the stl into Dwg or dxf CAD formats? Would it be better to mesh?

 

Okay so is the fluent meshing approach so different from the other one?

[Rob]

If you're using Magics or Simpleware there is/was a meshing tool embedded into the tool. That'll give a decent tet volume mesh. No idea about inflation as I've not spoken to their technical/development team in a fair while. 

Otherwise I'd be looking at Fluent Meshing (well, a colleague would - I've not quite figured out how the objects work) to remesh the surface, cap and volume mesh. 

[Valeria Guadagno]

Okay thank you! I'll try this way.

So you don't thing that converting the stl model into a CAD format would help?

[Rob]

It depends. Most of the stl's I see are too big or too complex for the skin tools. There's also an accuracy effect if the surface is "crinkled". 

[Valeria Guadagno]

Okay thank you for your help!