Geometry Tools

In many situations, the CAD geometry must be modified before the simulation can be run. In some cases, problematic entities such as sliver surfaces or extra edges can greatly complicate meshing. In others, the simulation model requires additional parts to simulate the flow. These can be either inside a cavity or a flow volume that completely surrounds the original model.

Geometry Tools provide a way to modify the CAD model for simulation.

• Edge Merging: Connect edges that share a vertex with an inflection less than a specified tolerance.
• Small Object Removal: Remove very small surfaces and edges that are typically too small to see, but can greatly affect meshing.
• Void Fill Creation: Fill an internal cavity with a meshable volume to simulate the flow.
• External Volume Creation: Immerse the model in a flow volume to simulate external flow.

To access the Geometry Tools, click Setup > Setup Tasks > Geometry Tools. Alternatively, right click on the Geometry branch of the Design Study bar, and click Edit...

Note: You should use Geometry Tools before assigning a mesh distribution. To use them after assigning a mesh or running, Autodesk Simulation CFD prompts you to remove the current mesh distribution.

When to Use Geometry Tools

The tabs are arranged in the recommended order of use:

Edge Merging --> Small Object Removal --> Void Fill --> External Volume

Note that using the tools in a different order may lead to unexpected results and possibly errors.

Apply Geometry tools before assigning any other model settings (boundary conditions, mesh sizes, etc.). This is because Geometry tools add and remove geometric entities from the model which may cause existing settings to be removed.

CAD and Model Requirements

The Geometry Tools are available for all Parasolid- and Acis-based geometry models as well as for Pro/Engineer geometry that has been launched using Granite.

The Geometry Tools are not available for Pro/Engineer launched with the Mechanica method. This is because the Geometry Tools change the underlying geometry. When the two methods are used, Autodesk Simulation CFD does not have direct access to the geometry, and cannot change it.

Geometry Tools are not available for meshed models imported into Autodesk Simulation CFD. These are fully meshed models that are either in Nastran (.nas or .dat) or Ideas universal (.unv) formats. They do not contain any geometry, so they can not be modified.

The Void Fill and External Volume tools are not available for 2D models.

The Undo Button

Each tool has an Undo button.

There are two levels of undo:

• To remove the most recent modification, click Undo once. (For example, if Small Object Removal was applied followed by a Void Fill region, click Undo to remove the Void Fill region, and leave changes made by small object removal.)
• To remove all other geometry changes, and to restore the geometry to its original state, click Undo a second time.

Note that after the mesh is generated, Undo restores the geometry to its original state.

Portability of Geometry Modifications

The modified geometry is stored in the Design Study in addition to the original geometry. A share file contains both as well.

Geometry Tools in a Design Study

Changes made to a geometric model persist when the design is cloned in the Design Study bar. The copied design has the same modifications as the original.