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Hi all,
I'm trying to simulate flow inside a cylinder with a hollowed-out core (annular cylinder).
Effectively, it will be a donut-shaped cross-sectional area flowing down a cylinder. A cylinder with a smaller cylinder subtracted?

Thank you!

Hi Hoon,

Thank you for your question, and sorry for the delayed response. Currently, there is not an easy way to make an annulus geometry in SimVascular, since SimVascular fills in the segmentations by default. We recommend using another software to construct your annular cylinder, then saving that as a VTK format file. SimVascular can then load in this VTK file to use for simulations.

Thank you Justin!
What software would you recommend?

If you have SolidWorks, I think it would not be too hard to create an annular cylinder and export the model as an .stl that you can load into SimVascular. I think there are also free CAD software like AutoDesk Inventor (this is the one I used for my CAD class 7 years ago... not sure if it is still free).

You can also try using Boolean operators in VTK if you are familiar with using it. An example on how to use Boolean difference operators can be found on this page: https://www.vtk.org/Wiki/VTK/Examples/P ... it/Boolean.

Thank you Justin. I will try. Would it be okay if I contacted you if I had problems?

Of course! I have not personally tried making an annular cylinder and it has been a few years since I have touched a CAD program, but I am happy to help in any way that I can.

Hi Justin,

I am doing patient specific modeling of cervical spine from MRI.
I used VolView, imported into SimVascular for path planning, segmentation, and mesh generation, and exported into STL. STL was then uploaded into Autodesk FUsion 360 for combine+subtract between two bodies, but I'm having problems. It appears that I first have to convert fro mesh to T spline in order to perform "Combine" and "subtract" or "Cut/cavity".
This is the message I got:

"This body contains a high percentage of triangles or n-sided polygons. Converting will result in a T-spline body that will not edit well and have poor performance.
For conversion to a T-spline body the mesh should consist primarily of four sided faces.

Mesh surface content:
Quads = 0
Triangles = 17212
Polygons = 0

Conversion has been aborted."

How do I get around this?
Thank you for your help.

Hi Hoon Choi,

I just responded to this here:

viewtopicPhpbb.php?f=188&t=7355&p=0&start=0&view=

Thanks!

SimVascular Development Team