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6.5.1 Grid Check Information

The information that FLUENT generates when you use the Check item will appear in the console. Sample output is shown below:

Grid Check

 Domain Extents:
   x-coordinate: min (m) = 0.000000e+00, max (m) = 6.400001e+01
   y-coordinate: min (m) = -4.538534e+00, max (m) = 6.400000e+01
 Volume statistics:
   minimum volume (m3): 2.353664e-05
   maximum volume (m3): 7.599501e-03
     total volume (m3): 2.341560e+00
   minimum 2d volume (m3): 4.027890e-04
   maximum 2d volume (m3): 1.230393e-03
 Face area statistics:
   minimum face area (m2): 1.300719e-04
   maximum face area (m2): 3.781404e-02
 Checking number of nodes per cell.
 Checking number of faces per cell.
 Checking thread pointers.
 Checking number of cells per face.
 Checking face cells.
 Checking bridge faces.
 Checking right-handed cells.
 Checking face handedness.
 Checking for nodes that lie below the x-axis.
 Checking element type consistency.
 Checking boundary types:
 Checking face pairs.
 Checking periodic boundaries.
 Checking node count.
 Checking nosolve cell count.
 Checking nosolve face count.
 Checking face children.
 Checking cell children.
 Checking storage.
Done.

The domain extents list the minimum and maximum $x$, $y$, and $z$ coordinates in meters. The volume statistics include minimum, maximum, and total cell volume in m $^3$. A negative value for the minimum volume indicates that one or more cells have improper connectivity. Cells with a negative volume can often be identified using the Iso-Value Adaption capability to mark them for adaption and view them in the graphics window. For more information on creating and viewing isovalue adaption registers, see Section  26.6. You must eliminate these negative volumes before continuing the flow solution process.

The topological information to be verified begins with the number of faces and nodes per cell. A triangular cell (2D) should have 3 faces and 3 nodes, a tetrahedral cell (3D) should have 4 faces and 4 nodes, a quadrilateral cell (2D) should have 4 faces and 4 nodes, and a hexahedral cell (3D) should have 6 faces and 8 nodes. Polyhedral cells (3D) will have an arbitrary number of faces and nodes.

Next, the face handedness for each zone is checked. The zones should contain all right-handed faces. Usually a grid with negative volumes will also have left-handed faces. Again, you cannot obtain a flow solution until you eliminate these connectivity problems.

The last topological verification is checking the element-type consistency. If a mesh does not contain mixed elements (quadrilaterals and triangles or hexahedra and tetrahedra), FLUENT will determine that it does not need to keep track of the element types. By doing so, it can eliminate some unnecessary work.

For axisymmetric cases, the number of nodes below the $x$ axis is listed. Nodes below the $x$ axis are forbidden for axisymmetric cases, since the axisymmetric cell volumes are created by rotating the 2D cell volume about the $x$ axis; thus nodes below the $x$ axis would create negative volumes.

For solution domains with rotationally periodic boundaries, the minimum, maximum, average, and prescribed periodic angles are computed. A common mistake is to specify the angle incorrectly. For domains with translationally periodic boundaries, the boundary information is checked to ensure that the boundaries are truly periodic.

Finally, the simplex counters are verified. The actual numbers of nodes, faces, and cells the solver has constructed are compared to the values specified in the corresponding header declarations in the grid file. Any discrepancies are reported.


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