Fluids

Fluids

Locate and fix left handed cells

    • admin
      Ansys Employee

      How can I locate and fix left handed cells?

    • admin
      Ansys Employee

      The mesh check report will indicate if the mesh contains left-handed faces and/or faces that have the wrong node order. If you have left handed cells and you are continuing the simulation without correcting it solver will calculate the face normal wrongly and that will result in wrong flux calculation. This may some time leads to divergence. You must take steps to repair such meshes, since you cannot obtain a flow solution until all of the faces are right handed and have the proper node order. 1. The left-handed faces mostly occur at locations where the surfaces that are non-conformally connected have sharp corners or contortions. When you get the left-handed faces, you can fix it in Fluent by the TUI commands: mesh/repair-improve/repair-face-handedness mesh/repair-improve/repair-face-node-order 2. When you fix the left handed faces you may get cells with negative volume. You will need to repair these cells manually. It’s best to fix the problematic geometry at the grid generation stage. To identify the problematic geometry, read the case file again and create an adaption register using the IsoValue Adaption panel with the category Grid and the subcategory Face-Handedness as follows: (a) Go to Adapt-->Iso-values (b) Select mesh in the Iso-value of drop down menu (c) Select Face handedness from the drop down menu below that (d) Enter 1 for Max as well as Min value in the Iso-min and Iso-max input box (e) Press mark (f) Go to manage in the same panel (g) Click on the display button to see where the negative volumes are forming This may give you an idea of the location of problematic geometry which you may then fix in the grid generation software.

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