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“Imprint” with Fluent Meshing and STL data

    • NickFL
      Subscriber
      I am working with a really terrible STL file and I am trying to mesh it using the meshing in Fluent (Fault Tolerant). I have worked through some simplified versions of my model and had no problems. But when working through the actual model, it is exhibiting a peculiar behavior.

      What is wrong, please see in the image below, is that when a surface mesh is created it does not go all the way to the tunnel walls. (I have created the bounding box to be 0 slack in the x and z directions). It seems like I am missing a step of imprinting the edges of the STL on the tunnel walls. The mesh on the tunnel walls is refined due to the proximity of the surface. But without the surface going all the way to the tunnel walls, the resulting volume mesh allows a shortcut for the flow to avoid contacting the surface. Of course this means a lot of fluid will take this path with less resistance.

      I am currently using 23R1 but have experienced the same problem in an earlier version. That is why I feel I am missing a step that was not necessary in my simplified models.
       
      When I shrink the tunnel walls to be only 90% (using -0.05 for the External Flow Boundary Box Parameters), the mesh goes to the walls, but sometimes these "flowers" form as extensions past the bounding box. One is shown in the image below on the left side. The xmin boundary is shown and there is a protrusion beyond it. Again I think this is a consequence of missing the imprint step.
      Another attempt was made trying to do the imprint in SpaceClaim just locks the computer up.
       
      Thank you for your time and any insight you can provide.
    • Federico Alzamora Previtali
      Subscriber

      I would try to use a fine wrapper size to ensure that it captures as many small features as possible in your model. 

      There is no "Imprint" feature in FTM but you can use Extract Edge task to identify important (existing) edge features 4.8. Extracting Edge Features (ansys.com).

       

       

      • NickFL
        Subscriber

        Federico, thanks for the advice. I had tried to play around with the extract edge feature, but it does not seem to keep interesection of the two faces despite them showing up quite well in the preview of the edge-group. It still creates a channel at the tunnel wall. I am excited about how well the mesh in the rest of the domain looks, it is just at the tunnel walls I am having difficulty with.

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