Extracting faces for vessel wall model in SimVascular

[Tanmay Shidhore]

Hello,

I am trying to import a solid geometry of the blood vessel wall with non-uniform thickness into SimVascular to perform FSI simulations and I am having issues extracting faces from the stl model. Some of the faces on the inner and outer walls are being extracted out even when a large separation angle is specified and it is proving to be difficult to merge them with the parent surface, as they are very small and not easily visible. Is there a method to extract faces in SimVascular other than specifying a separation angle? Alternatively, is it possible to import the model in a different format, like step/iges? I have tried to import iges models but SimVascular crashes every time I attempt to do so. Thanks.

[David Parker]

Hi Tanmay,

Upload your STL model to DropBox and I'll take a look. Also upload the STEP / IGES files, I'd like to understand what is causing SimVascular to crash.

Cheers,
Dave

[Tanmay Shidhore]

Hi David,

I have attached the link to the OneDrive folder containing the stl and iges files for the fluid and solid domains.

Link: https://purdue0-my.sharepoint.com/:f:/g ... w?e=eChzug

I have experienced the issue of SimVascular crashing while importing iges geometries with the latest version (19.01.27) as well as the one before that. When I try to import the iges file, SimVascular only displays one patch of the surface and crashes. This is the terminal output in mbilog when I attempt to import iges (screenshot attached)

[David Parker]

Hi Tanmay,

I had a look at the STL files, they are pretty awful, lots of seams, which is typical of STL files exported from CAD. These guys will need to be remeshed to produce a more regular polygonal mesh.

The IGES and STEP files do indeed fail to load, not sure what is going on here, the fault is deep down in OpenCascade, the open source CAD software we use. How did you create the IGES files? Do you have a Parasolid .xmt_txt file for these models?

I also tried to mesh the IGES files using gmsh but it failed, complained about some bad faces.

Cheers,
Dave

[Tanmay Shidhore]

Thanks David. I will try to remesh the STLs and check if that helps with the issue of small faces getting separated out. For manipulating STLs and creating the IGES files, I have used Geomagic Design X, which allows me to export in Parasolid text format and I have uploaded both .x_t files to the OneDrive folder.

[David Parker]

Hi Tanmay,

I was able to read the Parasolid file into SV but it could not extract the faces correctly. SV models are assumed to be built from lofted surfaces bounded by planar caps, that is how SV builds models, and that is how faces are identified.

I think it would be easiest for you to create a good polygonal surface (no holes, gaps or intersecting surfaces) from your model and import that into SV.

For my part I will look into making it easier to import models into SV, maybe add the capability to manually select faces.

Cheers,
Dave