Meshing issues on a very thin bag
 

Hi everyone,

I am fairly new to this forum, and this is my first post, so please forgive any rookie mistakes I may make :).

I am trying to run a fluent simulation of a liquid inside a thin plastic bag, exactly like the blood bags you would find in a hospital. The thickness of the bag wall is 0.0127cm (5 mil), and for the sake of the simulation the bag is approximated as an elliptical cylinder.

The thickness of the plastic bag walls in uniform throughout, and the top and bottom of the elliptical cylinder are flat.

When trying to mesh my geometry, the bag fails to mesh due to it being so thin. The error I am receiving states: "Patch-conforming tetrahedron mesh failed because of an edge intersection in the boundary mesh."
I have read through some ANSYS documentation on meshing and tried other techniques such as sweeping mesh, multizone, layered tetrahedron, and creating a midplane within the wall of the bag and meshing that surface; but had no luck.

I can create the mesh by making the element size very small, but this creates over 200k elements and I am unable to run that with my license.

I think it is important to note that I only have a student license of ANSYS and do not have access to ICEM.

I am stuck trying to figure out how to mesh the thin plastic bag, so if anyone can assist or provide some other resources I can read up on it would be greatly appreciated.


Thanks in advance!

For such a geometry I would advice to sweep the mesh from the end surface, when using Ansys Meshing (not Fluent meshing). Then make sure to select the end/start surface as your "source", as the program might not auto detect this properly.