Problems in initial meshing and mesh refinement most commonly arise in the following situations:
Importing geometry from external CAD tools. Occasionally the files used to transfer the geometric data are dirty on export from other tools. The resulting geometric inconsistencies can cause trouble during meshing. Typically these inconsistencies present themselves as problems in initial meshing but they occasionally appear later in the AMR process as the mesh is refined.
Complex models, especially when many solids exist in close proximity. Occasionally unintentional gaps are created which prevent the geometry from being meshed. Care must be taken to properly align solids prior to Booleans, etc.
The following conditions are of particular note:
Sliver Faces: Occur when the ratio of the length of the shortest edge to the longest edge of a face in the geometry (the aspect ratio) of a mesh element exceeds an internal tolerance. These are rarely intentional and often a result of misaligned solids.
Short Edges: Occur when very short edges are found in the geometry. These are rarely intentional and are often the result of misaligned solids.
These conditions are not always catastrophic to the meshing process, but they may lead to low qumay ality mesh, thereby slowing down the convergence of the finite element solvers. Some problems could also produce incorrect physics and cause simulation failure.. If Analyst detects such conditions it will proceed if it can, but generate a warning message. If it cannot proceed it will generate an error message and meshing will stop.
Analyst provides assistance in determining where these and other conditions are located as described in the next section. It is often possible to fix sliver faces and short edges by altering the geometry slightly to correct misalignments. Even if the simulation continues, it is always a good idea to adjust the geometry to eliminate the issues.