Creating a Geometry for Analysis

Overview of Geometry Modeling Concepts

In COMSOL Multiphysics you can use solid modeling or boundary modeling to create objects in 1D, 2D, and 3D. These can be combined in the same geometry (hybrid modeling).

•	During solid modeling, a geometry is formed as a combination of solid objects using Boolean operations like union, intersection, and difference. Objects formed by combining a collection of existing solids using Boolean operations are known as composite solid objects.

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Boundary modeling is the process of defining a solid in terms of its boundaries — for example, using lines to create a solid hexagonal domain in 2D. You can combine such a solid with geometric primitives — common solid modeling shapes like blocks, cones, spheres, rectangles, and circles, which are directly available in COMSOL Multiphysics.

In 3D, you can form 3D solid objects by defining 2D solids in work planes  and then extrude  and revolve these into 3D solids. It is also possible to embed  2D objects into the 3D geometry.

You can also overlay additional nonsolid objects on top of solid objects to control the distribution of the mesh and to improve analysis capabilities. For example, you can add a curve object to a geometry to control the element size in the vicinity of this curve, or add a point to guarantee a mesh vertex in a specific location or to create a time-dependent or parametric-value graph at that location in the geometry.

The settings for the nodes making up a geometry sequence can be changed at any time and the whole sequence can be re-run. It is also possible to parameterize the geometry using one or more parameters that define properties of a geometric primitive, for example. COMSOL then takes the parameterization into account as part of the geometry sequence for each step in a parametric sweep. You can also insert geometry sequences from other models into your current sequence. In general, you can use an expression that contains numbers, mathematical functions, and global parameters to define the dimensions and location of the geometry objects, work planes, and other geometry nodes.

You can import 2D geometries from DXF files and 3D geometries from STL and VRML files.

See Import for details of how to import these CAD file formats.

The CAD Import Module provides an interface for the import of CAD files in Parasolid, SAT (ACIS), Inventor, Pro/E, SOLIDWORKS, STEP, and IGES formats. In addition, the CATIA V5 Import Module provides an interface for CATIA V5 files.

The optional LiveLink™ products offer bidirectional links to 3D CAD software. Using these, you can run parametric geometry sweeps driven from the COMSOL environment but operating directly on the geometries in the respective CAD package.

• Working with Geometry Sequences • Creating a Geometry Sequence • Geometry in the COMSOL Multiphysics Programming Reference Manual

The Introduction to COMSOL Multiphysics includes a tutorial to learn how to build the busbar geometry. See Appendix A — Building a Geometry or the printed copy included with COMSOL Multiphysics.