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A significant amount of the CFD solution time is spent on geometry clean-up and meshing and it would be a relief for CFD practitioners to save this time to some extent. According to the NASA CFD Vision 2030 Study, CAD interoperability and access to geometry, mesh adaptation and high-order mesh generation, mesh generation kernels, and automated mesh generation are key topics that require due consideration and commitment.
For now, the below-mentioned 10 steps can ease the preprocessing step (primarily importing CAD files and meshing) for a CFD solution using the Fidelity Pointwise meshing software.
1. Import Native CAD File: The ability to import native CAD formats is bundled with every Fidelity Pointwise license. Importing native CAD directly avoids the need for an intermediary-neutral format.
Figure 1. Hydraulic oil filter geometry imported from Solidworks.
2. Check the Integrity of the Solid Model: An important benefit of using native CAD files is the ability to retain the solid model. Fidelity Pointwise can import the solid model and exploit the available information, which includes details on how the surfaces are stitched together. Even when using native CAD files, it is a good idea to check to see if the solid model is watertight.
Figure 2. Checking the integrity of the solid model in model assembly.
3. Reorganize Surfaces: The complementary capability to Fidelity Pointwise’s solid modeling is quilting. Quilting allows the user to redefine the meshing regions from the original CAD surfaces to something more meaningful.
Figure 3. Before quilt assembly(left), after quilt assembly (right).
4. Set Meshing Defaults: Once a solid model with a logical arrangement of meshing regions is ready, then we can apply an unstructured surface mesh to the model. To facilitate this, some default meshing parameters need to be set.
5. Mesh the Model: Now that the meshing parameters are set, the model can be meshed. Fidelity Pointwise will create one surface mesh for each quilt created in Step 3.
Figure 4. Surface mesh of the model.
6. Adjust the Resolution of Surface Meshes: Setting default meshing parameters helps create the appropriately refined surface meshes in the initial creation, but there are often instances in which some additional adjustment of the surface mesh is warranted, such as increasing the internal edge length or reducing the resolution of the surface, etc.
7. Assemble Unstructured Block: Creating a volume mesh in Pointwise is a two-step process. Since the surface meshes are watertight, block assembly is straightforward.
8. Generate Volume Mesh with T-Rex: The second step in the volume meshing process is to initialize the block, and for resolving the boundary layer near the surface, Pointwise T-Rex meshing is used.
Figure 5. Initializing the T-Rex volume mesh.
9. Set CAE Boundary Conditions: Prior to exporting the mesh to a CFD solver, the CAE boundary conditions need to be set up, and this task is performed in an analogous manner.
Figure 6. Setting CAE boundary conditions.
10. Export CAE Files: The final step is to export the mesh. CAE export contains a critical feature when using T-Rex volume meshes called prism combination. Although the T-Rex algorithm only generates tetrahedral elements, it stores information that enables the combination of triplets of adjacent boundary layer tetrahedrons into one triangular prism.
For a full mesh generation workflow using Fidelity Pointwise, watch the YouTube video below:
For more information, refer to the article ‘From CAD to CFD in Five Minutes: The Complete Story of Meshing a Real Geometry Using Fidelity Pointwise’ by clicking the button below.