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Adding Triangles to an Unstructured Domain Based on Surface Curvature

Adding triangles to an unstructured surface mesh is generally needed when the underlying database surface is highly curved. We can add triangles based on the curvature of the database surface without changing the grid point distribution of the connectors. Begin with an existing domain that does not adequately follow the curved surface upon which it has been created.

Note that the numbers in the following steps apply to the example database; you will need to find out what dimensions best work for your geometry.

Example of a highly curved database surface Surface mesh no clustered to curvature

With a connector average spacing of 1.0 set in the Defaults tab, the domain to the right was created automatically by selecting the database surface and clicking on Domains on Database Entities on the toolbar. However, the resulting domain created by only using the connector spacing default does not follow the surface curvature very well.

Maximum Angle

To see how setting the Maximum Angle and reinitializing the domain can improve the appearance of the domain, follow these steps.

Surface mesh clustered to curvature with maximum angle
  1. Select the domain.
  2. Grid, Solve
  3. Attributes
  4. Notice that Surface Shape is checked and that the shape is database constrained. In the Target Database Selection frame, also notice that the number of Database Entities Picked is equal to one, which refers to the underlying surface that has been automatically chosen.

  5. In the Triangles frame, uncheck Not Applied under Max. Angle.
  6. Enter 10.0 for Max. Angle.
  7. Apply
  8. Solve
  9. Initialize

The domain looks much better and you can see that about 45% more triangles were added as a result of the Maximum Angle setting. Also notice that the grid point distribution on the connectors was untouched because only the domain was modified.

Maximum Deviation

To see how setting the Maximum Deviation and reinitializing the domain can improve how closely the domain conforms to the curved surface, follow these steps.

Surface mesh clsutered to curvature using maximum deviation
  1. In the Triangles frame, check Not Applied under Max. Angle.
  2. Solve
  3. Initialize
  4. You now have reset the domain with the default attributes.

  5. Attributes
  6. In the Triangles frame, uncheck Not Applied under Max. Deviation.
  7. Enter 0.04 for Max. Deviation.
  8. Apply
  9. Solve
  10. Initialize
  11. Click on OK to exit the Grid, Solve menu.

The domain has still improved from the original domain created with only the connector spacing set. For this case, about 40% more triangles were added to the surface mesh. But notice that though the domain has changed, there does not seem to be much of a difference between the uses of the Maximum Angle setting versus the Maximum Deviation setting.

Whether you use Max. Angle or Max. Deviation to add triangles depends on the database surface. As a suggestion, test the use of both settings at different times to see what works for every unique surface.


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If you have questions about the steps outlined above or on any other meshing topic, please contact us via one of the following methods.

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