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Method to ensure a coherent mesh - all vertices of adjacent cells merges into one node

Alexander Fikri

Hi MSC Apex forum

I am meshing a CAD model for use in a neutronic simulation in PHITS, a Monte-Carlo particle transport software. PHITS is really specific with meshes and will not accept the mesh if adjacent tetrahedra are converging into a single node, as depicted in the attached image.

I would like to know if I could fix this with either of these solutions:

  1. Using a feature in MSC Apex that is applied globally to force convergence of vertices for every adjacent cell. I tried meshing the assembly at once rather than on a part-by-part basis, but this problem will still occur
  2. Identifying the problematic nodes and fixing them manually using the node move feature. To do this, I will have to identify the specific cells that are problematic using their CTETRA numbering as shown in the image below. How do I isolate cells based on their CTETRA numbering in MSC Apex?

Thank you

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     I'm a little confused by what you mean when you say, "adjacent tetrahedra are converging into a single node". Do you want tets on adjacent bodies to meet or not meet at shared nodes, or is the issue something else?

    Rohit's suggestion to use Node Merge is worth trying. Another approach is to Boolean Unite your parts with "Merge Solids as Cells" checked. In Apex, different solids have meshes that do not match, but a single solid divided into multiple cells will have a continuous mesh. By selecting Cells in the pick filter when meshing, you can set different preferred sizes for each cell. Apex's use of the terms parts, solids, and cells may be different from what you're used to.

    Regarding finding problematic nodes, you want the Probe tool with Label Methods: Label By ID.

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  • 0

     I'm a little confused by what you mean when you say, "adjacent tetrahedra are converging into a single node". Do you want tets on adjacent bodies to meet or not meet at shared nodes, or is the issue something else?

    Rohit's suggestion to use Node Merge is worth trying. Another approach is to Boolean Unite your parts with "Merge Solids as Cells" checked. In Apex, different solids have meshes that do not match, but a single solid divided into multiple cells will have a continuous mesh. By selecting Cells in the pick filter when meshing, you can set different preferred sizes for each cell. Apex's use of the terms parts, solids, and cells may be different from what you're used to.

    Regarding finding problematic nodes, you want the Probe tool with Label Methods: Label By ID.

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