Defeaturing Streamlines the Simulation Process
Once the CAD model has been properly repaired, it may still be difficult to use in a simulation due to the complexities of the geometry and the number of small geometric features in the model. Some of these may have resulted from the CAD modeling process itself, like small faces, slivers, spikes, and short edges, for instance. Other features may be required for eventual manufacture, such as fillets, grooves, threads, and holes, but are basically irrelevant to an overall simulation of the CAD model. In both cases, the presence of these small features will usually lead to a concentration of the mesh to adequately resolve them. For the sake of saving on computational resources, they should be removed and replaced by a uniformity in the geometry to reduce the required meshing.
The CAD Import Module provides features to assist with this defeaturing through identifying them, and either automatically or manually removing them to streamline the simulation process. For unintentional features, such as slivers, you select their type in an interface, specify a tolerance value, causing all occurrences of this geometric feature to be identified in your geometry. From here, you can manually specify the features to be defeatured. The CAD Import Module will then remove them, generating a smooth or uniform geometry for better meshing. Defeaturing can also be performed automatically as part of the import process, utilizing the same tolerances specified for repairing.
For intentional features that would still require a lot of mesh resolution, such as holes and grooves, you can manually select their geometric position in the geometry, and choose to fill, cap, patch, or delete them. That prompts the CAD Import Module to replace them with a uniform surface, through filling or patching.
Virtual Operations Concentrate Simulations to Regions that Matter
For other geometric features that you wish to avoid or remove from the meshing and simulation processes, you can apply Virtual Geometry Operations to concentrate your simulation activity to regions that matter. These allow you to select entities in regions of your model that do not influence the simulation greatly, or are not particularly relevant to the desired simulation, and request the mesher to ignore them. The meshing subsequently takes place on a virtual geometry. Such operations involve ignoring vertices, edges, and faces, forming composite edges and faces, and collapsing edges and faces. These operations are included in the base package, COMSOL Multiphysics, and are a great complement to the defeaturing tools of the CAD Import Module. This is very useful functionality particularly when the features of the geometry cannot be easily removed through defeaturing or repair, or when the simulation requires you to keep the curvature of the geometry intact.
Geometry Repair Gets Your Simulations Started
Producing CAD models is a robust, while not exact, science. Often the goal of creating the CAD model is visualization and specification of tolerances and materials to be read off by the manufacturing team or engineer tasked with changing an existing device or process. It is quite common that the CAD model is not exact with respect to adjacent faces meeting at the same exact point in space. Very small and hardly noticeable anomalies can occur throughout the CAD model, creating non-physical objects or regions that can lead to difficulties when meshing within COMSOL Multiphysics. Therefore, geometry repair is always performed by default during the import process to get you started with your simulations.
The CAD Import Module provides features that allow you to automatically detect and, either manually or automatically, repair your CAD models. While it may be preferable for the design engineer to perform some of the repair job in his or her CAD tool, the CAD Import Module will identify where these anomalies exist as they may not be immediately discernible from within the CAD program. Alternatively, you can manually select adjacent faces within the CAD Import Module and knit them together to form a solid, or specify tolerances in the import process, allowing the CAD Import Module to perform this automatically.
LiveLink™ Products Provide Further Functionality
The CAD Import Module provides all the tools you need to adequately communicate data between your CAD model and your COMSOL geometry. All of the functionality is also available in the LiveLink™ products, which provide you with an even tighter integration of CAD design and simulation. With the LiveLink products you can optimize the CAD model geometry from within your simulation model.
The key feature enabled by the LiveLink products is the synchronization between COMSOL Multiphysics and your CAD system. Not only does it allow for the import and export, geometry repair, and defeaturing of CAD models, but also the geometric associativity between a geometry in COMSOL Multiphysics and a CAD model in your CAD system. This means that changes in one immediately result in the update of the other, through the synchronization feature. You avoid the import/export and re-importing of the entire CAD model once you have identified a change to be performed in the CAD model due to a change in your simulation. Additionally, parametric sweeps can automatically be run based on a geometric entity such as the length of an edge. Any definitions of physics in your geometric domains or on your boundaries are retained irrespective of the changes that have occurred in the geometries.
The capabilities mentioned here are available inLiveLink™ for AutoCAD®, LiveLink™ for PTC® Creo®Parametric™, LiveLink™ for PTC® Pro/ENGINEER®, andLiveLink™ for Solid Edge®. LiveLink™ for Inventor® andLiveLink™ for SOLIDWORKS® have an added functionality that allows for you to perform your COMSOL Multiphysics simulations from within the GUI of these two respective CAD tools.
All trademarks listed herein are the property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. For a list of such trademark owners, seehttp://www.comsol.com/tm.