Meshing ErrorModel or Geometric Query Failure

Mar 3, 2012


Issue:

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: Model query failure for surface A near X Y Z

Error: Geometric query failure for edge A near X Y Z

Solution:

Solution

Throughout the mesh generation process, the geometry is measured and evaluated to determine placement of nodes and elements. This error means that Autodesk® Simulation CFD was unable to complete one of these evaluations, and was therefore unable to generate the mesh. This is a general failure of a model query, and examples include a failed projection or derivative calculation.

1. Find the problem location

After the failure, an orange dot is drawn on the model at the coordinates listed in the error message. This is the location at which the meshing process stopped. The model is shown as transparent and the offending volume is selected to help you find the problem location:

  • The orange dot may be difficult to see, so turn off the mesh seed points to improve visibility. (From the menus at the top of the User Interface, click Window, and uncheck Show Mesh Seeds.)
  • Click the View as Outline icon to turn off all shading. This can really help you to see inside the model.
  • Since the problematic volume is selected, note the ID for future reference. Adding it to a group (right click, and select Group > Create group) is a convenient way to quickly access the part later.

Surface and Edge Diagnostics are also very helpful for finding the problem:

  • On the Meshing dialog, click the Diagnostics button.
  • Move the slider to identify small entities that may be problematic.

2. Inspect and repair the geometry at or near the problem location. 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 

The Geometry Tools (Edge Merging and Small Object Removal) can fix many of these problems. (Right click on the Geometry branch of the Design Study bar.) If these tools are unable to resolve the problem, return to CAD system to fix the geometry.

3. 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.

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).

4. 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.

5. Refine the mesh

If the problem location is on an edge or surface, try refining the mesh distribution locally. This is more efficient than refining an entire volume, and will prevent the mesh count from getting as big. 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).

 

Products:

Simulation CFD

Versions:

2010;2011;2012;2013;2014

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