Gridgen - Pointwise's Legacy Meshing Software
Gridgen is Pointwise's legacy software, used by engineers and scientists worldwide since 1984 to reliably generate high quality grids for CFD.
Flexible CAD Interoperability
Interoperability of computer aided design (CAD) models (or the lack thereof) poses significant challenges to the CFD practitioner. Other meshing software forces analysts to interface directly with the CAD system, tying up a valuable software asset and requiring significant software training. Gridgen provides a flexible suite of CAD data access methods, allowing the analyst to select the optimum approach.
Solid Meshing Recovers Engineering Topology
One approach to working with complex geometry models in Gridgen is Solid Meshing. This technique involves recovering the "engineering topology" from the rather arbitrary CAD topology. The engineering topology reduces a geometry model to major components relevant to meshing like wings, blades, and sidewalls. This is accomplished using tools that provide solid model import and creation.
Once a solid model of the geometry has been created, all the seams between adjacent surfaces are closed and meshing can proceed without having to deal with special issues related to gaps and overlaps.
Read more about how solid modeling simplifies the geometry and makes it easier to mesh.
Fault-Tolerant Meshing Eliminates CAD Healing
Another problem with CAD model interoperability is sloppy geometry such as gaps between adjacent surfaces, overlapping surfaces, and missing features. An analyst must be able to mesh a less than perfect model. Even though other software attempts to "heal" the CAD model through a variety of manipulations, healing is an ill-defined problem since design intent is usually unknown. Using a technique called Fault Tolerant Meshing, Gridgen is able to create a fully closed mesh on a sloppy CAD model. Merging automatically identifies adjacent surface meshes, joins them across CAD model gaps, and uses the mesh solver to remove CAD artifacts such as topology and sliver surfaces from the mesh.
Gridgen does not require the use of a CAD model for meshing - the mesh can be created directly in 3D without having to create geometry first. This feature lessens dependence on the CAD system, allowing the analyst to use CAD geometry only where necessary. Furthermore, Gridgen's geometry modeler may be used to supplement the CAD model and create new models from scratch:
Also, Gridgen's hybrid geometry kernel allows models to be imported in de facto standard formats such as PLOT3D wireframes and STL triangular faceted data.
When meshing complex CAD models, Gridgen can create meshes that are independent of the CAD topology. A mesh may span an entire CAD surface, only a portion of a surface, or multiple surfaces.
Read more about how Gridgen ensures your geometry is analysis ready whether it is analytic or faceted.
Direct CAD Access
Through a partnership with CADNexus, a direct method for obtaining CAD data without translation is available for Gridgen users. CAPRI2NMB is a CAPRI CAE Gateway application that works directly with a CAD system's native kernel. Gridgen's native NMB geometry file is produced automatically by direct queries into the CAD model. The NMB file is then simply imported into Gridgen. Because CAPRI2NMB works directly with the CAD software, it has the potential to provide more robust geometry transfer. CADNexus supports CATIA V5, Pro/E, UG NX, SolidsWorks, Parasolid, and OpenCASCADE.
For more information about CAPRI2NMB including licensing information, please contact CADNexus directly. Contact information is available at www.CADNexus.com.
Structured Hex Grids
Structured grids containing mapped hexahedra or quadrilaterals are initialized using transfinite interpolation (TFI) algebraic techniques and adhere automatically to the CAD model wherever possible using standard, linear, polar, and orthogonal TFI, and parametric and parametric fit TFI.
The quality of structured grids can be significantly improved by applying Gridgen's elliptic PDE methods. These methods iteratively solve Poisson's equation. While the defaults have been set to provide the nominal grid, the control functions can be fine tuned at any time using the following techniques:
Structured grids with high degrees of orthogonality and clustering control can also be created using Gridgen's hyperbolic PDE and algebraic extrusion methods. All of the extrusion methods can be applied to 2D grids, surface grids constrained to CAD surfaces, and volume grids. The hyperbolic method is especially well suited for CFD solvers that use overlapping grids but contains features to extrude multi-block abutting grids as well.
Overset Grid Assembly Integration
Gridgen interfaces directly with overset grid assembly (OGA) software packages PEGASUS5 and SUGGAR including customized interfaces for hole-cutting setup and launch. The OGA results are imported as IBLANK data including fringe, hole, and orphan objects. You can then control the display of all these objects throughout the gridding process in order to ensure that your overset grid will result in an accurate CFD solution.
Unstructured & Hybrid Meshes
Unstructured and hybrid mesh generation offer fast, highly automated methods for generating a CFD mesh. Gridgen provides several methods from which you can choose the one most appropriate to your analysis.
Anisotropic Tetrahedral Extrusion
Anisotropic tetrahedral extrusion, otherwise known as T-Rex, is a technique for extruding regular layers of high-quality tetrahedra from boundaries. The tetrahedra can be recombined into prisms if you prefer. The mesh adjusts to convex and concave regions and colliding extrusion fronts.
An optional post-processing step combines a stack of three anisotropic tetrahedra into a single prism, reducing cell count and providing an even higher quality cell in the near-wall region.
Here are more resources for learning about T-Rex.
Direct Prism Extrusion
Prism layers are created by the extrusion of triangular surface grids following normal, linear, rotational, or user-defined paths with control over extrusion step size or aspect ratio.
Tet Generation with Delaunay Methods
Unstructured grids consisting of triangles and tetrahedra are generated by a modified Delaunay method. Like structured grids, unstructured surface grids can span multiple entities in the geometry model and adhere to the CAD model automatically. The unstructured solver may be re-applied at any time, giving you control over minimum and maximum cell size, maximum cell-to-cell turning angle, maximum surface deviation, and boundary decay.
These attributes may also be set in advance to result in a good grid automatically. Edge swapping and Laplace smoothing may also further improve unstructured surface grids.
Automate & Customize Meshing
Gridgen's Tcl-based scripting language, Glyph, provides customization capabilities for both the experienced analyst and the "design engineer". The experienced analyst will find that Glyph's commands cover the entire range of functionality available in Gridgen's GUI, allowing tricks and special techniques to be captured and made part of the organization's intellectual property. Designing engineers will appreciate the fact that Glyph may be used to create customized meshing applications for specific configurations, allowing them to automatically generate a mesh and apply CFD.
Journal Your Session for Editing Playback
Glyph scripting is complemented with a journaling capability. Gridgen exports the Glyph form of each GUI command to a file for later editing and playback. Journaling is further complemented with variables, name-value pairs that may be defined and utilized in the GUI so that a journaled Glyph script can be easily edited for parametric variation of a baseline mesh.
Share Scripts with the Community
The Glyph Script Exchange is a forum for sharing Glyph scripts with the entire Gridgen community. Dozens of scripts are available for download that add unique capabilities to Gridgen. Your scripts can be uploaded for everyone to enjoy.
Read more about Gridgen's Glyph scripting in this article.
Using the industry-standard OpenGL® graphics API, Gridgen's interactivity and 3D graphics are available on a variety of Windows® (Intel® and AMD®), Linux® (Intel® and AMD®), Mac®, and Unix® (SGI®, HP®, and Sun®), workstations, all with the same look and feel and transportable Gridgen native file. Gridgen's graphical user interface (GUI) guides engineers through preprocessing, eliminates extraneous menus, and uses a consistent menu system and nomenclature for the entire process, from CAD model import/creation through volume grid generation and analysis software file export. When combined these features make Gridgen easy to learn, easy to use, and easy to remember how to use.
Other features of the GUI are:
Gridgen supports Windows on both AMD and Intel.
Gridgen supports Linux on both AMD and Intel for both 32-bit and 64-bit.
Linux installations must include:
Under RedHat Enterprise Linux 5 (32 and 64 bit) the specific libraries and the package from which they may be installed are listed below. (For other Linux distributions, we recommend using rpmfind.net to determine which packages to install.):
A recommended minimum platform configuration is:
To configure overlays and other graphics options for your graphics card, please refer to your card vendor's documentation.
Gridgen may run on Linux platforms other than the one recommended above if the required libraries are installed. For users of OpenSuse 10.2 and 10.3, the additional package, compat-f77, may be necessary for Gridgen to run properly.
*Up-to-date graphic accelerator driver software is essential for proper operation of Gridgen.
CFD Solver Interfaces
Gridgen supports neutral, native, and de facto standard interfaces to CFD solvers (including the specification of solver boundary conditions), grid files, and geometry formats to ensure that Gridgen fits into your CFD process.
Grid and Flow Solver Data Export
Grids and flow solver data (e.g. boundary conditions) can be exported from Gridgen to the following formats.
Grid Import and Export
Just the grids themselves can be imported and exported to and from a variety of formats.
Geometry Import and Export
Geometry on which the grid will be generated (database in Gridgen's vernacular) can be imported from and exported to a variety of formats.
Read more about Gridgen's interoperability in this article.
If you have never used Gridgen before, you will prefer Pointwise. Gridgen is included with every Pointwise license to provide greater utility to existing Gridgen users when they make the transition to Pointwise.
Call to Action
Better, faster meshes start with a free trial. Request one today and begin putting Pointwise to use.