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[FAQ]

With a non-conformal interface, the following warnings can appear: “Warning: Failed to correct face handedness”, or “left-handed faces detected” during Mesh Check or Initialization It means that it has generated left-handed faces and negative volumes. If you continue to solve with such a warning, then the normal vector of the intersected mesh will point in the wrong direction, and could cause an issue in terms of computing any flux terms on intersected faces. These left-handed faces are mostly appearing at locations where the surfaces, that are non-conformally connected, have sharp corners or contortions. At some points in such locations, the two surfaces could actually be passing through each other. In such a case, nodes projected from one surface to another, during the creation of the non-conformal interface, connect in a reverse loop leading to left-handed faces. To overcome this problem try: 1.Reverse the order in which the surfaces are picked inside the Grid Interfaces panel while creating the non-conformal interface 2. Try the TUI command /mesh/repair-improve/repair (with /mesh/repair-improve/repair-face-handedness yes) 3.If that doesn’t work, look carefully at the two surfaces involved especially at corners and turns. Modify the mesh to make sure that the two surfaces are not passing through each other at any point. The generated left-handed faces can be located by creating Iso-surface of Mesh->Face-handedness (Value = 1. Face-handedness is a parameter that is equal to one in cells that are adjacent to left-handed faces, and zero elsewhere). Using iso-surfaces rather than contours is suggested, since it might not be possible to see contours of face-handedness, since these faces lie on the non-conformal interface which is not available for plotting contours. Once these faces are located, go to Fluent Meshing (or another meshing software) and read in the mesh *saved before making the non-conformal interfaces* and fix corners/contortions close to the identified locations.