About Geometry, Topology, and Connection Checkers

Geometry checkers verify that there are no problems with model geometry that might that prevent you from creating a valid FEM representation and mesh. For example, nonmanifold edges (that is, edges that join more than two faces) cannot exist in a solid part. For example, the central edge joining the three surfaces in the image below is a nonmanifold edge.

Similarly, sharp angles between faces are undesirable, because they create narrow or distorted mesh elements. The geometry checkers highlight these problems so that you can make corrections before generating a mesh.

Topology checkers search the model surfaces for self-intersections, discontinuities, or thin faces. Such features are never ideal but might be acceptable (or ignored) for manufacturing and other uses of the design. However, mesh generation accounts for all the model topology, so these features are likely to cause problems as you create a mesh and prepare your model for simulation.

Self-intersections are surface features that return onto or extend through themselves. Any calculation or process that relies on the proper identification of the interior or exterior of a face (such as contact) is likely to fail if there is self-intersection.

Discontinuities are surfaces or surface features that have an abrupt change in position. For example, an edge that seems continuous but in fact contains a small break.

Thin faces are any faces that are small in one dimension relative to the overall model size. They often overly restrict mesh generation, creating distorted elements or using a nonpreferred element type to mesh the thin face.

Topology problems are often artifacts of the process used to create the CAD model. However, you must resolve topology problems so that they do not create problems in the simulation.

Connection checkers verify whether you can join adjacent surfaces in your model. The checkers search for edges within a minimal distance. Typically, you use the default search distance that the app calculates for your model. If you change the search distance, you must use a distance that is less than the length of the smallest edge or surface in the model.

The checker lists any edges with gaps smaller than the search distance, and you can highlight each set of edges that is creating a gap to see the problems in the model. You can transfer the edges that the app finds into a geometry set. You can then use the healing tools on the geometry set to resolve the issues and repair your geometry.

Joining surfaces and healing gaps in the model removes unnecessary constraints from the mesh. Gaps and the edges of unjoined surfaces are treated as geometry features. Mesh generation creates element edges constrained along these features, just as it does on the real edges in the geometry. Joined surfaces and healed gaps create continuous surfaces, typically creating a smoother mesh that is better for simulations.