26.17.1 Checking the Mesh

Figure 26.17.3: The Mesh Tab in the Case Check Dialog Box

The following recommendations appear under the Mesh tab (Figure  26.17.3):

• Check your mesh.

  If you have not already checked your mesh, it is best practice that you do so immediately after reading in your mesh, or after any mesh modification. To check your mesh go to

  General Check

  Checking the mesh will help you detect any mesh trouble before you get started with your problem setup. You can learn more about the information obtained when checking your mesh, by going to Section  6.5.

• Improve the mesh quality before proceeding with your simulation. The maximum cell skewness is greater than 0.98.

  Check the quality of your mesh immediately after reading in your mesh, or after any mesh modification. The quality of the mesh plays a significant role in the accuracy and stability of the numerical computation. You can learn more about the quality of your mesh by going to Section  6.2.2.

  General Report Quality

• Preview zone motion and mesh motion before beginning the simulation.

  After setting up your case using the Dynamic Mesh model, it is worth while to preview your mesh prior to running your simulation. You can preview Zone Motion by going to

  Dynamic Mesh Dynamic Mesh Display Zone Motion...

  To preview the Mesh Motion, go to

  Dynamic Mesh Dynamic Mesh Preview Mesh Motion...

  Run Calculation Preview Mesh Motion...

  It is important that you preview zone motion first and then mesh motion. Zone motion shows the motion of all dynamic zones with the prescribed rigid body motion, using the graphics library. It is a very fast process and does not alter the mesh. Previewing the zone motion will show you if the motion is setup properly (e.g. zones moving in the wrong direction or rotating about the wrong center). It is much more difficult to detect these problems with mesh motion because small time steps are performed and no continuous animation is shown.

  Mesh motion should always be done for dynamic mesh cases with prescribed motion. Mesh motion will only show the validity of the mesh during the simulation. Mesh deformation and dynamic zones without rigid body motion will be considered during a mesh motion preview.

  Both the Mesh Motion and Zone Motion dialog boxes will have a Preview button which will allow you to view the mesh or zone motion prior to running your case. You can obtain more information on mesh motion and zone motion by going to Section  11.3.10.

• Translate the mesh for axisymmetric geometry containing nodes below the x-axis.

  If either Axisymmetric or Axisymmetric Swirl is specified in the General task page and there are mesh nodes that fall below the X-axis, then it is recommended that you translate the mesh. 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. To find out if there are any nodes that lie below the x-axis, perform a mesh check (Section  6.5). For information on translating the mesh, see Section  6.8.12. To access the Mesh Translate dialog box, go to

  Mesh $\rightarrow$ Translate...