A Meshing Toolkit for Physics-Based Solvers



The CAD2Mesh software was developed by a team at the Rockwell Science Center starting in the mid-1990s due to a need for unstructured and structured volume meshing capabilities. The meshing software, called “UNISG” at the time, was used by Rockwell scientists on a number of high profile projects, including B1-B store separation and space shuttle return to flight applications. It has been used in the development of many physics-based solvers at HyPerComp.


The CAD2Mesh software is currently implemented using an object-oriented C++ architecture using standard open libraries for the GUI and 3-D graphics, allowing for porting to all graphical flavors of Linux as well as Windows.



FEATURES





Fast transition from large blue-light scan data to surface/volume meshes for high end multiphysical solvers



Automatic CAD repair tools to minimize processing time/labor for creating water-tight models



Generation of high-order curvilinear surface and volume meshes consistent with high-order solvers in creating large cell sizes with geometric fidelity to minimize computing resources for large-scale problems



Template approach for quick turnaround grid generation with automated parametric geometry creation for design and optimization of complex problems



Mesh
- Surface (quad, triangular and hybrid elements)
- Volume (structured and unstructured)



Geometry creation, manipulation and repair
- Auto repair
- Shrink-wrap mapping (gaps/overlaps and small features removing)Establish watertight surface connections



Boundary condition set up and Template design tool
- Turbo-machinery
- Helicopter blades
- Hypersonic wave rider and Busemann inlet design



CAPABILITIES





IMPORT, EXPORT, CREATION AND MANIPULATION





CAD models may be imported into CAD2Mesh via IGES, STEP, or Plot3D surface files. Complex CAD entities such as trimmed surfaces and STEP assemblies are supported.

A wide variety of functionality for the creation and manipulation of points, curves, and surfaces is available.
Shell entities may be used to represent collections of surfaces forming solids. A surface mapping technique allows the user to force surfaces to adhere to other underlying surfaces. This may be used to change surface topology or perform CAD repair. Geometry may be organized into “regions” for visibility, grouping, boundary condition, and meshing purposes. Geometry may be exported as IGES or Plot3D style surface data.



CAD REPAIR





Automated CAD repair operations are available for fixing common geometry errors and de-featuring small or interior parts. For instance, many small trimming loops representing rivet holes may be removed at the push of a button.

Larger CAD errors may be repaired using CAD creation and manipulation functionality.

Our CAD repair capabilities allow the user to make changes to the underlying geometry without the need to return to the CAD software or involve CAD designers.



SURFACE AND VOLUME MESHING





High quality triangle and “paved” (all quad or mixed triangle and quad) watertight unstructured surface meshing, as well as structured meshing is available. Mesh resolution or fidelity may be specified in a number of ways, including automated techniques.

Unstructured volume meshing is performed using an advancing front algorithm that grows tetrahedral or pyramidal cells within a closed volume. Structured and semi-structured zoning is available and all volume meshing types may be combined to create a single global grid.




FACET CONVERSION





Geometry is becoming readily available in facet formats. This presents a challenge since most mesh generators, including CAD2Mesh, are built upon a parametric geometry kernel. Facets must first be converted into parametric surfaces.

A number of semi-automated operations are available in CAD2Mesh for performing facet conversions, including creating curves on facets and mapping curves and surfaces to underlying facets.





HIGH-ORDER MESHING





Higher-order vertices are generated for surface elements on the target geometry as well as for off-body faces that touch the surface. Bending off-body faces is used to prevent cell faces from crossing each other. Cell faces are represented as temporary parametric NURBS surfaces with higher-order coordinates obtained from these surfaces at desired parametric locations using existing functionality contained in the CAD2Mesh geometry kernel.




ADAPTIVE MESHING





Initial adaptive surface meshing techniques have been implemented within CAD2Mesh. The method splits surface elements at higher order geometry quadrature points according to either geometry curvature error, solver results or both. Multiple refinement or splitting levels are utilized. The algorithm then reconnects the elements to ensure watertightness and smooths the resulting refined mesh. This method has shown significant savings in mesh size over ad-hoc refinement methods.




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