What's New in Gridgen

Gridgen V15.17 - March 2011

The T-Rex hybrid mesh generation technique now supports baffles. Baffles have been available in Gridgen for use in isotropic tet grids for a long time. Baffles are just surface meshes that provide cell size control or model thin surfaces. When baffles are added to a T-Rex mesh, layers of tets (and prisms) are grown off the baffles to resolve off-body features.

Gridgen's algorithm for reducing cell count in a T-Rex mesh by combining stacks of three aniostropic tets into a single prism has been expanded and now works across block boundaries. In some cases this has reduced overall cell count in the final grid by 29% over previous versions of the software.

Gridgen V15.16 - August 2010

The addition of overset grid assembly (OGA) capability to Gridgen represents a substantial leap in functionality for the Version 15.16 release. The overset feature suite provides the ability to set OGA parameters, launch the OGA software, and import and visualize the results. PLOT3D import capabilities have been expanded significantly to include single block, IBLANK, big/little endian, and 2D, all of which are detected automatically upon import. The T-Rex hybrid meshing technique's ability to combine tets into prisms was vastly expanded by removing restrictions when you use the multiple normals feature at convex boundaries or when your initial surface mesh has quad cells. By lifting these restrictions, your cell count can be reduced further, in come cases by 28 percent. Gridgen now is built as a Mac universal Binary and includes native support for Intel-based Macs running OS X 10.4 or later, including OS X 10.6 (Snow Leopard). Gridgen's integration with overset grid assembly software means holes, fringe and orphans can be visualized readily and the grid immediately adjusted as needed to ensure a good CFD solution.

Gridgen V15.15 - November 2009

The size of hybrid meshes generated by the T-Rex technique for anisotropic tetrahedral extrusion was reduced by up to 57 percent by increasing the scope of tet-to-prism combination in the extruded near-wall regions. Premature termination of prism combination due to mesh quality issues was avoided through the addition of a second pass in order to account for both the quality of the extruded tets and the quality of the cells created as a result of tet combinations. In addition, more robust handling of extruded layers near symmetry planes and the addition of diagonal swapping on the symmetry plane mesh further improves the scope of cell recombination.

Gridgen V15.14 - June 2009

Hybrid mesh quality was improved in the anisotropic tetrahedral extrusion (T-Rex) technique. Mesh skewness reduction improvements include vertex decimation and step size attenuation in concave regions and addition of extrusion points in convex regions. Anisotropic to isotropic transition was improved through vertex refi nement, enhanced handling of colliding extrusion fronts and seeding the isotropic mesh with points generated by the extrusion algorithm.

Gridgen V15.13 - November 2008

Anisotropic tetrahedral extrusion has been accelerated by a factor of up to 7. Prisms can be extracted from an aniso tet block at any time rather than just in the solver. The Gridgen fi le can be imported into Pointwise where a new prism extraction algorithm combines more tets into prisms resulting in up to 40 percent fewer cells.

Gridgen V15.12 - August 2008

Anisotropic tetrahedral extrusion has been accelerated by a factor of up to 10. The Delaunay (isotropic) tet mesher can now handle meshes where surface edge lengths vary by more than six orders of magnitude. The anisotropic unstructured surface mesher has been extended to better handle highly curved surfaces. This change also improves the robustness of the isotropic tri mesher. Gridgen's CGNS export is now consistent with Pointwise's CGNS capabilities: face-based data and 2D elements zones for BC regions. A new metric function for Examine, volume ratio, provides a measure of the volume (or area) variation between adjacent cells.

Gridgen V15.11 - December 2007

The NCRs in V15.11 support Pro/E Wildfire 3, Seimens PLM (formerly Unigraphics) NX 4, and CATIA V5 R17 SP4. Platform support for HP-UX has been added. The Examine command can now be customized to either recall or ignore the last examined function on a mesh. Gridgen's license manager was updated for compatibility with Pointwise. Now both can be served from the same license fi le.

Gridgen V15.10 - March 2007

A new technique has been added to the block unstructured solver: anisotropic tetrahedral extrusion. This technique offers the capability to generate high aspect ratio (i.e. fl at) tetrahedra with included right angles near the boundary. Starting from a surface mesh of triangular cells, the cell height at the wall, and a growth rate, tetrahedra are extruded layer-by-layer. Tet extrusion stops locally when the cells become isotropic. Tet extrusion also features collision detection and will locally stop extruding where two layers will collide due to geometric proximity.

As a postprocessing step, aniostropic tets can be combined into prisms so that cell count is reduced by a factor of three. Finally, a surface implementation of anisotropic tetrahedral extrusion is available for generation of triangular meshes. Also available in V15.10 are export of native Tecplot files and direct CAD interfaces via CADNexus' CAPRI software.

Gridgen V15.09 - February 2006

Solid models from CAD can now be imported, created, and meshed in Gridgen, providing an adjunct to the software's current fault-tolerant approach. Computations for merging and joining adjacent meshes over gaps in the CAD model (the Auto Merge and Auto Join options for the On DB Entities command) are more automatic using pre-existing solid models. The relative proximity of database surfaces can now be measured using the Examine command to support the assembly of solids in Gridgen.

Interfaces were added for FIELDVIEW Unstructured v3, Cobalt unformatted, the FrontFlow CFD solver and the "bread" command is now written to STAR-CD input files. Gridgen was ported to the SGI Prism and the software now is fully certifi ed for both Windows and Linux on AMD Opteron.

Gridgen V15.08 - July 2005

Solution times for smoothing structured grids were decreased by up to a factor of 15 with the addition of a multigrid solution algorithm to the elliptic PDE solver. An update of Gridgen's graphics engine for compatibility with newer graphics cards has yielded a 15-50 percent increase in graphics performance (frames per second) across all platforms. The Unigraphics Native CAD Reader now supports version NX3.

Gridgen V15.07 - April 2005

Commands to create trimmed surfaces and add or remove edges have been added. Trimming lost during CAD file translation can now be recovered easily. More complex and realistic models can be created directly in Gridgen using trimmed surfaces. Using the new IGES file export, analysts can save their analysis- ready geometry, including layers, names, colors and other organizational data, in a CAD-standard file format for re-use in other CAE disciplines.

Gridgen V15.06 - December 2004

Gridgen is now available for use on the Apple iMac and Power Mac platforms running Mac OS X. Two new features expanded the scope of meshes that can be generated using the extrusion algorithms. Hex and prism meshes can be extruded simultaneously from structured and unstructured domains, respectively. Also, existing surface grids can be used as the boundary condition for a new extrusion. Adjacent extrusions can differ in height, but still match point-to-point along their common boundary.

Gridgen V15.05 - September 2004

Gridgen is now delivered with a native Itanium version built on HP-UX 11.23. Gridgen's Native CAD Readers have been upgraded to support Unigraphics NX2 and Pro/ENGINEER Wildfi re 2. Gridgen's Glyph scripting language can be extended by linking with a library of C routines (compiled as dynamic libraries).

Gridgen V15.04 - May 2004

Unstructured surface meshes respond more robustly to changes in connector grid point distribution. Instead of losing their 3D shape, points are now inserted into the domain and automatically smoothed. An interface to the Star-CCM+ CFD solver was added. Layer manager functionality was extended through the addition of right click commands.

Gridgen V15.03 - March 2004

The Replace command was added to Merge Entities for control over which of the two connectors to keep while merging. A native interface to Wind-US (the unstructured version of the WIND CFD solver) was added for both single and double precision. A double precision option was added to the Cobalt interface while at the same time its memory usage was decreased.

Gridgen V15.02 - December 2003

Gridgen's fault-tolerant meshing of sloppy CAD geometry now provides enhanced visual feedback of where gaps in the database have disrupted the mesh topology. Instead of repairing the CAD model, Gridgen's Merge tool closes the mesh across CAD gaps using both global and local tolerances. A double precision option was added to the NSAERO CFD solver interface.