In this tutorial, you will create a fully unstructured tetrahedral mesh around a car-body
geometry imported as an IGES file. This tutorial illustrates the steps you would typically
follow to prepare an imported CAD geometry for meshing. The IGES-file contains “dirty”
geometry—that is, gaps exist between some of the surfaces that make it unsuitable for
creating a CFD mesh. You will clean up the geometry using the GAMBIT “tolerant modeling” capability. The tolerant modeling option automatically assigns a tolerance value to
each imported vertex and edge to maintain topological integrity for the imported model.
The original CAD geometry is not modified during the import process.
The imported geometry includes a number of small surfaces, the edges of which may
unnecessarily constrain the mesh generation process. Using the “merge faces” command,
GAMBIT allows you to easily combine these surfaces prior to meshing. You can then
have GAMBIT automatically create a triangular mesh on the car body.
Since the imported geometry consists only of the car body, you need to create a suitable
domain around the car in order to conduct a CFD analysis (this is loosely equivalent to
placing the car in a wind tunnel). The remainder of the tutorial shows how to add a real
box around the car body, use virtual geometry to create some missing faces, and finally
stitch all faces together into a single volume. This volume can then be meshed (without
any decomposition) using a tetrahedral meshing scheme.
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