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Meshing issue on a very thin wall

    • dodonn4
      Subscriber

      Hello everyone,

      I am trying to run a Fluent simulation of a liquid volume contained in a thin plastic bag, exactly like a blood bag you would see in a hospital. The plastic bag is simulated as an elliptical cylinder with a wall thickness of 0.0127 centimeters (5 mil). When creating the mesh for this system, the mesh fails to generate on the plastic bag and the following error message appears: "Patch-conforming tetrahedron mesh failed because of an edge intersection in the boundary mesh."

      I can create the mesh by making the element size very small, but this creates over 200k total elements, which my academic license cannot handle. In addition, I have tried other techniques such as using a thin sweeping mesh, but had no luck and got the error: "The source and target face areas are dissimilar and therefore unsuitable for thin model sweeping. If the program generated source faces are not desirable, specifying the source faces manually may help."

      My main question of this post is if anyone knows of good meshing techniques that can be used for a very thin walled cylinder. If anyone could suggest some ideas or recommend some documentation for me to review, it would be greatly appreciated!

      Thanks in advance!

    • peteroznewman
      Subscriber
      The plastic bag geometry should be modeled as a surface, not as a solid. The fluid inside will be modeled as a solid body. After the fluid volume is defined, the plastic bag is simply the faces of the solid body that represents the fluid volume. Those are easily lifted off the solid body by a select, copy and paste operation in SpaceClaim. In Mechanical, the sheet body is meshed with shell elements that are assigned the material property and the thickness of the plastic film.
    • dodonn4
      Subscriber
      Thank you! This worked perfectly.
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