Fluent's next-generation preprocessor

Model generation, including geometry modeling and mesh generation, represents the major bottleneck in CFD analysis today. At Fluent, we recognize this issue and we have established model generation as a core technology in which we are investing heavily. The return on this investment will be new preprocessing tools with the power and ease of use that will greatly reduce your time to solution.

Currently, a large development team is hard at work on Fluent's next-generation preprocessor. Built upon a state-of-the-art solid geometry modeler, the new preprocessor unites powerful geometry and mesh generation tools with a clean, modern user interface (Figure 1) that is easy to learn and use. The new preprocessor is a tightly-integrated environment containing geometry modeling, mesh generation, and mesh quality diagnostics in a single application. Functions in all areas are organized in a clean, consistent, and logical manner.

Bringing Together Complementary Technologies

When Fluent and Fluid Dynamics International (FDI) joined forces in 1996, our complementary technologies for model generation were an important synergy between the two companies. The new preprocessor unites FDI's expertise in geometry modeling and automated hexahedral meshing with Fluent's strengths in tetrahedral and hybrid meshing. Well before Fluent and FDI joined forces, FDI had begun work on a next-generation preprocessor for its FIDAP product. At the same time, Fluent was extending its TGrid product with advanced hybrid meshing. (See article, page 15.) Continuing development of the new preprocessor is a collaborative effort with a single development team that includes developers from both the Fluent and FIDAP groups.

Toward Automated Model Building

The new preprocessor contains a variety of tools for generation of hexahedral, tetrahedral, and hybrid meshes. Using a range of algorithms, it provides both "automatic" meshing as well as more conventional user controls. To facilitate automatic meshing, the new preprocessor is designed to minimize problems associated with so-called "dirty" geometries, i.e., geometries with gaps and other mismatches between adjacent surfaces. By using a solid modeler and focusing on streamlining the cleanup of dirty surface geometries, we hope to minimize geometry issues as a bottleneck in the model building process.

Figure 1: This unstructured hexahedral mesh was generated automatically, given only a target element size. Unstructured tetrahedral meshing tools, from TGrid, are also part of the new preprocessor.

A Toolbox for Model Building

Some of the key features of the new preprocessor include:

• ACIS(TM) solid geometry modeler from Spatial Technologies Inc.
• Direct access to ACIS solid models from AutoCAD and other ACIS-based systems
• IGES and discrete geometry import (including STL)
• Automated geometry cleanup
• Complete journaling and playback
• Toolkit of mesh generators
• Structured and multiblock hexahedral/quadrilateral meshes with automated domain decomposition
• Unstructured, conformal, hexahedral/quadrilateral meshes with automated domain decomposition (Figure 1)
• Unstructured, nonconformal, hexahedral/quadrilateral meshes with embedded regions (hanging nodes) and boundary layers (Figure 2)
• Triangular surface meshes
• Tetrahedral volume meshes
• Prismatic layered meshes, pyramid transition elements for hybrid mesh generation

Figure 2: Automatically generated hexahedral mesh with embedded "hanging-node" regions. This meshing approach offers great promise for automation of meshing on complex geometries.

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