The first step in the CFD case preparation is the creation of the surface meshes. Initially, only the Surface Mesh tab is active as illustrated below:
The SM settings are described in the table below:
Min pixel size of selected structure |
Displays the pixel size [mm] in the data. |
Smoothing (FWHM) |
It is representing a Gaussian filter and allows smoothing the data before creating the STL structure. The default value corresponds to the pixel size in the data. It is recommended to use a smoothing value 3 times the minimum pixel size. |
Segmentation Threshold |
All pixels with the value above the threshold are included in the segment. The default value is 0.35. When the Optimal checkbox is enabled the threshold will be calculated automatically such that the volume of selected elements is preserved. |
Decimation |
Allows simplifying mesh by removing tringles from the surface mesh without changing the mesh. Please note that in this case the simplification procedure is done after the mesh is created. The value ranges between 0 and 1. The number represents the percentage of triangles to be thrown out. Usually a value of 0.5 is a good compromise. The smaller the number of triangles, the faster will be the 3D visualization. It is a slow procedure which generates smaller files. Decimation only changes the number of STL nodes, particularly the vertices of the surface mesh. However, no change in the mesh geometry occurs, preserving thus the mesh topology. |
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When enabled allows saving the generated STL file in the surface-meshes folder. This folder is located in the directory set as Case path (local) in the PGEM configuration settings. The SM STL files stores information related with the Bounding Box and Point in mesh location. This information is used for the calculation of the VM. |
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When enabled shows the SM generated based on the definition of the cutting planes |
Define boundary condition plane |
When enabled allows starting the definition of the cutting planes. The cutting planes definition is mandatory for the CFD simulation. When disabled allows creating SM for visualization purposes. Such SM are used to create VM of selected geometries for visual presentations and cannot be used for CFD simulation |
In the example above the Smoothing was set to 3 mm while the default settings were used for decimation 0.5 and segmentation threshold 0.35. Toggle the Save and the Display checkboxes in order to save and preview respectively the result of the definition of the cutting planes.
Enable the Define boundary condition plane checkbox to start the definition of the cutting planes.
Two methods are available for the definition of the cuttings planes: Preview and 3D. Enable one method radio button followed by the activation of the Generate surface mesh green button.