Imported CAD files are automatically converted to the format of the Parasolid® 3D geometric modeling engine within the Design Module. You can then use the Design Module to change and manipulate them. For instance, you can create a domain around a CAD design for subsequent modeling and analysis. While a CAD model can represent the geometry of an object to be manufactured, you may be more interested in simulating the environment surrounding it. Thus, you need to define an appropriate geometry to represent this environment.
The Design Module is built on the proven parametric framework for generating geometries in COMSOL Multiphysics® and on the industry standard Parasolid® geometric kernel. Thereby, it enables modifying or constructing designs from the ground up and sharing them with other tools.
In addition to the geometric operations found in the CAD Import Module, you can also create lofted objects based on cross-sectional profiles and use operations such as fillet, chamfer, midsurface, and thicken. For example, by using the loft tool, it is possible to create geometries from slices or contours, such as from an MRI scan. Creating fluid volumes inside imported solid objects also becomes a lot easier by using the cap faces tool.
Repairing the Geometry Manually or Automatically
You can always perform geometry repair when importing a CAD design into the Design Module – even by default. Geometry repair ensures that non-physical regions, which would prevent COMSOL Multiphysics from meshing the imported file, have not been introduced to the modeling process.
The Design Module contains tools to detect and repair your CAD models, where small anomalies, such as adjacent faces not intersecting at the same point, may exist. Anomalies can either be knitted together manually or automatically through setting tolerances as part of the import and repair process. If you prefer to repair the CAD model in your CAD tool, it may not be very easy to identify where the anomalies exist. You can use the Design Module to find them first.
Defeaturing Models to Augment Better Meshing and Simulations
A repaired geometry can still contain geometric features that make it difficult to either mesh or perform robust simulations. In particular, small features may concentrate large numbers of mesh elements in regions where changes in the simulation results are negligible and can thus be ignored.
The Design Module contains tools for identifying and defeaturing by removing certain features, such as spikes, holes, slivers, short edges, and small faces, for example. Like the repair operations, these features can be identified and removed in your CAD tool, or by the Design Module, manually or automatically.
Other defeaturing tools allow you to identify difficult-to-mesh features, such as grooves, and to cap, patch, fill, or delete them. An example of re-parametrizing a geometry is when imported fillets are inconsistent for simulation. These fillets can be identified and defeatured, and then, using the fillet operation in the Design Module, new parametric fillets can be included.
Virtual Operations Concentrate Simulations to Regions that Matter
Virtual Geometry Operations are a useful tool within COMSOL Multiphysics that provides better meshing analysis solutions. This is done through instructing your meshing tool to ignore selected entities and features, thereby avoiding concentrating meshing in these regions – the meshing is taking place on a virtual geometry.
The ignored regions would typically be part of the geometry where your simulation results are uniform or irrelevant to your particular situation. You can use Virtual Geometry Operations to ignore edges, vertices, and faces; subsequently form composite objects; or collapse the entities.
These operations are included COMSOL Multiphysics and augment the geometry manipulation capabilities of the Design Module. Particularly, when certain features are difficult to remove through the Design repair and defeaturing tools.
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