Geometry Creation and Import with COMSOL Multiphysics by Layla S. Mayboudi

Author:Layla S. Mayboudi [Layla S. Mayboudi]
Language: eng
Format: epub
Publisher: Mercury Learning and Information
Published: 2019-06-10T16:00:00+00:00

7.2 GEOMETRY-FEM COMPATIBILITY

Another important feature of a commercial FEM tool is the method by which it interacts with the imported geometry from a third-party CAD commercial software package. As briefly mentioned in the earlier sections, the designer who creates the geometry in the CAD tool may “perceive” that they did a good job when creating the solid part—meaning that their design standards are met. However, the same file imported to the FEM tool may not meet the standards of the hosting environment. There are errors in creating the geometry in the CAD tool that may go unnoticed even by the most expert designers. They may focus on the correct application of the dimensions, relative positions of the components with respect to each other, or subpart interaction within an assembly. However, they may not necessarily ensure that the line and area connections at the vertices are made perfectly and at the correct locations.

The FEM specialist, however, is aware of such error types and can detect them if they have come across a number of troubled geometries in their geometry manipulation dossier. As geometries get more complex, detecting and providing solutions to address the geometry discrepancies become assets to the project. On occasions, the FEM specialist may decide to simplify the geometry to the bare necessities or create a new one—for example, the negative of the part when modeling air flow within a channel—to make the geometry suitable to the FEM tool and also to expedite the analysis process. They may have to think outside the box (or the square) depending on the analysis dimensions. They can then experience the pure joy of seeing the predictions made based on their virtual model validated by a physical mock-up.

Since in a majority of scenarios the commercial FEM software developers cannot compete with the dedicated commercial CAD tool developers in either geometry creation or manipulation, they either partner with some—making it possible for their users to employ the geometry kernel directly in the program—or simply cannot afford this union—meaning they do not have a built-in kernel—and opt for interfacing applications that can be employed as a bridge between the FEM program and chosen CAD tool in order for the geometries to be imported under certain conditions. The concept of geometry-tolerance imports and modifications so that the geometry is accepted and meaningful to the hosting program may be better explained with the following analogy.

Imagine a guest entering the house on a rainy day. The host may ask them to take their shoes off as the host does not tolerate the dirt that may be brought in by the wet shoes—tolerances need to be defined for the geometry import. The host also asks the guest to leave their dripping umbrella outside the door—geometry may need to be defeatured or simplified. Those are the host conditions that assure that the guest-host interactions are respectful of the limitations and therefore doable. Now what if the guest has a soaking wet pet? The host may provide a towel for the pet to be wrapped around and dried; they may also provide some booties.

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