Meshing ErrorGeneral ErrorMesh Failure on an Invalid Model

Mar 3, 2012


After setting up the analysis model and starting the simulation, the process stops during the meshing stage and one of the following errors is given:
Meshing Error: Error Code 60

Meshing Error: Error Code 715

Meshing Error: Mesh cannot be generated on an invalid model. (Code 1001)

Meshing Error: Meshing Failure

Error: Model definition in the vicinity of surface ## is suspect. This may affect meshing.

During the generation of the mesh, a problem either in the geometry or the mesh definition prevented the mesh from successfully generating. There are several things that can cause this error to be issued.



1. Adjust Mesh Enhancement

The problem might be due to overlapping Mesh Enhancement layers. On the Meshing dialog, click the Enhancement button, and reduce the Layer Factor to 0.3.

2. Inspect and Reduce the Minimum Refinement Length

The Edge Diagnostics are a great way to identify potential problem areas. Edges that are really tiny are pointed out, and often indicate where geometry problems are. To use Diagnostics:

  1. On the Mesh Sizes dialog, click the Diagnostics button.
  2. Select the Edge tab.

If this step points out a geometry problem, then skip to step 3.

Otherwise, reducing the length scale can help with the mesh by better accounting for very small geometric details. To make this adjustment:

  1. If you see several arrows on the model, slide the Highlight Edges slider to the left until most disappear. (If you don’t see a lot of arrows, this step won’t help.)
  2. Start by reducing the value by half.
  3. Click the Use highlight length button.

Note: Reducing the length scale will likely cause more elements to be generated (and as a result, a longer analysis time).

3. Inspect Surfaces using Surface Diagnostics

The Surface Diagnostics are a powerful tool for identifying problematic surfaces. Slivers, surfaces with "cusps," and other irregularities are identified with this tool. To use Surface Diagnostics:

  1. On the Mesh Sizes dialog, click the Diagnostics button.
  2. Select the Surface tab.
  3. Slide the slider toward the left to progressively highlight the smaller surfaces.
  4. To write surface IDs that are problematic to a text file, click the Save to text file button. This creates a convenient reference when fixing the model in the CAD system.

4. Inspect and repair geometry

Some things to look for include:

  • Surfaces that overlap or are on top of one another
  • Tiny gaps between surfaces or volumes
  • Sliver surfaces
  • Tiny volumes resulting from volumes that overlap
  • Edges that are shared by more than two surfaces 

Applying the Geometry Tools (Edge Merging and Small Object Removal) can fix many of these problems. If that doesn’t work, return to CAD system to fix the geometry.

5. Refine the mesh

This is a little tricky because this error does not give much guidance about where the problem location is. Start with any areas from the previous steps that appear too coarse. Areas highlighted by the Edge and Surface Diagnostics are also a good place to refine.

Start with either surfaces or edges (but not both so as not to over-refine the mesh). Do this by:

  1. Open the Mesh Sizes dialog. (Right click off the model and click Edit…)
  2. Change the selection mode to either Surface or Edge. (Right click off the model, mouse over Selection type, and select the desired mode).
  3. Select the surfaces or edges in the model that will be refined.
  4. Move the Size adjustment slider toward Fine (between 0.75 and 0.9 is a good place to start)
  5. Click the Apply button in the Size adjustment group.
  6. Repeat as needed with other entities.
  7. Click Spread Changes when you are finished with your adjustments.
  8. If refining on edges or surfaces does not work, try refining on volumes (between 0.75 and 0.9 is a good value to begin with).

6. Disable mesh boundary layer blending

This control adjusts the way Mesh Enhancement layers transition throughout the model, and is a "flag" control. To invoke this setting, add this item to your cfdesign_flags.txt file, located in the Autodesk® Simulation CFD installation folder.

mesh_boundarylayer_blend 0

Tests have shown that this setting can allow for successful mesh generation.



Simulation CFD