Centerlines and Boundary Layer

[Saeid Talaei]

Dear SimVascular Developers,

I am going to simulate a cerebral aneurysm which includes a few branches with different diameters using SimVascular. While I was doing the mesh generation procedure, I faced two problems.
At First, I wanted to use the radius based meshing. When I checked the created centerlines, all the branches had their own proper centerlines; however, the aneurysm itself had none. Consequently, the quality of the mesh in the aneurysm was poor and the geometry was not detected well around it. It would be great if you could help me how to create a centerline inside the aneurysm.
Secondly, as I know, to produce the boundary layer mesh, the global edge size parameter is just needed (not the local edge size of each branch). As a result, the boundary layers of the smallest branches will have high thickness. In contrast, the largest branches will have low thickness boundary layer. As you know, having these kinds of geometries with different branch sizes is very common in vascular models. Thus, I was wondering if you could tell me how to locally adjust the boundary layers according to the diameter of each branch.

Kind Regards,
Saeid

[Adam Updegrove]

Hi Saeid,

Thanks for the post! Because the aneurysm does not have a cap, you cannot currently generate an additional centerline into the aneurysm. However, you can still specify a local mesh size by selecting a surface and setting a smaller mesh size, or using regional refinement using a sphere region. Go to the "Regional Refinement" tab in the SV Meshing module, and highlight the box next to "Sphere" move and resize the sphere around the aneurysm, then click "Add" and specify a better mesh size for the aneurysm.

As far as having a boundary layer where the thickness is varied based on vessel size is actually a feature that is currently under development. Stay tuned and hopefully we will have this in the next release of the software.

Thanks!

SimVascular Development Team

[Saeid Talaei]

Dear Mr. Updegrove,

Thanks for your response.
Based on the discussion we had before, I have recently seen that you have changed the Simvascular’s source “https://github.com/SimVascular/SimVascular”; I think that those changes are related to “Centerline” and “Boundary Layer Meshing” issues. I have two questions as follows:
1) Based on the changes you have made, is SimVascular capable of producing a proper centerline in aneurysm and boundary layers variable in accordance to the diameter of each branch now?
2) Is the SimVascular source ready to be compiled with new features now? When would be the approximate time for the next release of binary file of software?
Thanks again.

Kind Regards,
Saeid

[Adam Updegrove]

Hi Saeid,

Yes, good eye. I recently implemented this new feature into the SimVascular source code. The centerline extraction will still be the same, but the boundary layer will now scale with the size of the mesh at the wall. So, if you choose to do radius-based meshing, then the boundary layer will scale with the radius of each vessel by default.

If you compile the current source, these changes will be in the built source.

The development team needs to discuss about the next binary release of the software. We do not have a specific date set at this point in time.

Thanks!

SimVascular Development Team