CAD Repair

CAD data for CFD is usually generated as part of the manufacturing design process and often is not of the quality needed for CFD. Today’s geometries, used in CFD analysis, are comprised of large assemblies which may have been constructed using multiple CAD packages, and potentially corrupted by layers of translation. Assemblies may even be generated to different tolerances in different CAD packages. Merging geometry to a clean volume is one of the most difficult challenges in the CFD process.

Ennova takes a fresh perspective to this problem. Dirty geometry is often very difficult to fix and to make it watertight often means a lot of remodeling or manual surface editing. Ennova does not translate the model, it leaves geometry in its native format with native readers (maybe complete model is from multiple CAD sources). Ennova forms a database of the geometry model to which the mesher can pass queries. No geometry is changed or fitted and multiple CAD formats can be handled this way without translation.

Ennova creates an intermediate layer between the mesh and the original CAD data. This layer can be envisioned as a shrink-wrap or referred to as the topology of the model. This topology is initially created from the CAD geometry and assumed not watertight. Automatic rules are then applied to make the topology water-tight which is usually successful without further effort. However, should the topology need further control (either from the need to be water-tight or extra resolution needed in the simulation model ) the normal manual CAD repair process can be used. Applying this methodology enables the meshed topology to be guided by the CAD model but not dependent on how the CAD model is constructed. Regardless, all cleanup is performed on the topology and the underlying geometry is left unchanged. The xyz coordinates in the original CAD data are always the same as in the mesh.

Not all the information in the CAD model is needed for meshing. The CAD repair in Ennova is intelligent in that it is controlled by the meshing algorithm in that it only cleans up what it needs to mesh. And after cleanup it checks the final geometry to make sure it is able to be cleanly meshed. This way the final clean geometry is not only geometrically clean but clean in the sense it will create a valid mesh.