2.2. Extracting FW4 CAD surface

The SALOME Geometry module is designed for:

  • Import and export of geometrical models in IGES, BREP, STEP, STL, XAO and VTK formats;
  • construction of geometrical objects using a wide range of functions;
  • viewing geometrical objects in the OpenCASCADE (OCC) viewer;
  • transformation of geometrical objects using various algorithms;
  • optimization of geometrical objects;
  • viewing information about geometrical objects using measurement tools;
  • designing shapes from sketches;
  • defining fields.

The Geometry module includes many GUI features and functions that enable basic CAD modelling and allows importing several standard CAD interchange formats listed in a table below.

Format Short description
BREP Used to store 3D models and is part of Open CASCADE Technology (OCCT)
STEP Standard for the Exchange of Product model data
IGES Initial Graphics Exchange Specification - vendor neutral file format of CAD model
STL File format native to the stereolithography
XAO CAD file format

In this tutorial we will create surface CAD models of ITER blanket obtained from ITER design office. From these defeatured models we can then create meshes required for SMITER field line tracing.

Before launching SMITER we need to ensure that STEP files are available for import and some intermediate study files for later tutorials by

make -C study/step
make -C study/tutorial

or look under the location pointed by environment variable $SMITER_STUDY_EXAMPLES_DIR for ITER-Blanket.stp that we will be importing shortly.

Note

In continuation we will be referring to the files provided under the study/ directory that may also be provided as a system-wide read-only source of examples provided with SMITER under $SMITER_STUDY_EXAMPLES_DIR for tutorial and/or resources for testing and starting points that should appear in dialog box as a shortcut.

2.2.1. Importing geometry

We start SMITER and start a new case by clicking ont the Geometry module icon geometry_module_icon where we select New.

../_images/geom_1.png

With Geometry module activated we import a STEP file ITER-blanket.stp through menu File ‣ Import ‣ STEP that is located under study/step directory as described above. This STEP file of around 200MB was exported by CAD “modeller”. STEP is a standard CAD data interchange format. After the file was read the following question appears

../_images/geom_2.png

to which we respond by No and then it will take several minutes to interpret all geometrical entities described inside. The “import” process is quite commonly long as the CAD kernel is interpreting the commands and builds the model in the same manner as it was designed by performing necessary geometric operations and checking for occlusions and trimming of algebraic surfaces by boundaries prescribed.

By clicking on the “eye” icon_visiblemesh in front of assembly name tele0654... we show or hide selected object. When icon_visiblemesh is enabled then by clicking on Fit All icon the assembly appears completely. Since this is a group of many parts it appears in a grey color.

../_images/geom_4.png

By selecting the assembly object it will appear highlighted and then from the menu New Entity ‣ Explode we select Solid Sub-shapes Type.

../_images/geom_5.png

By clicking Apply and Close and confirmation with Explode the shape containing 552 sub-shapes will be created. The exploding operation may take few minutes to complete as it is creating a new modelling tree that can be seen in the study.

We will assign Auto Color property by right clicking on newly exploded assembly that has now “eye” hidden and will appear in different colors shortly.

By clicking on the first wall panel number 4 the it is shown as selected in white and can be found highlighted under name FW_BODY somewhere in the middle of the Object Browser. We can then rename it to FW4_BODY by double click on the name or F2 for easier identification later on.

../_images/geom_7.png

By right-click on the panel 4 again we select Show Only to continue working on this object in sequel.

../_images/geom_8.png

We are only interested to extract plasma facing surfaces for meshing. This includes edges that may be hit by particles. At this point it may be good to save the study somewhere with File‣Save As. It can be observed that the file saving and opening is much faster than importing. Because the modelling tree does not need to be checked or interpreted also reading models from HDF study files is quick comparing to STEP import. The size of binary HDF study is half of the STEP file in ASCII format.

It is also a good practice to leave everything in study in order to see complete data at some later time and be able to modify the case for additional studies. Although only FW4_BODY is shown when saving, everything is saved, except the view on the data that follows usual hierarchical principles of display.

2.2.2. Selecting plasma facing surfaces

At this point we may continue or open the study/tutorial/geom1.hfd file and again select FW4_BODY to be on the Show Only.

By having FW4_BODY selected we again create New Entity ‣ Explode. We change Sub-shapes Type to Faces. By presing Apply and Close and confirming explosion then 217 faces are created.

With Shift and mouse click we select faces including edges as shown on the following image.

../_images/geom_9.png

From these face selection we now create New Entity ‣ Build ‣ Shell and change shell Name to FW4.

../_images/geom_10.png

After Apply and Close new shell appears at the bottom of the Object Browser. We may wish to change the color of the panel and save the study at this point before proceeding to create a mesh from the newly created FW4 shell or continuing with the shell extraction on the remaining panels.

../_images/geom_11.png

The study with extracted FW4 is available as study/tutorial/geom2.hdf. We will be using FW4 as a target on which power deposition will be calculated by firstly computing incidence angles and shadowing effects i.e. “wetted area” on the panel of interest.

Unless we continue extracting shells and create the whole set of panels we can now simply File ‣ Import ‣ STEP the whole first wall shell available as study/step/ITER-inner_wall_surfaces_sides.stp.

../_images/geom_12.png

Note

When enabling FW4 and newly imported first wall for one segment complete first wall we see shadow and target overlapping each other at different areas. These slight differences are due to display approximation only and does not affect actual shape processing and meshing that is accurate at time of operation. The quality of display approximation is controlled by File‣Preferences‣Default deflection coefficient. Changing from default 0.001 to 0.0001 will increase display precision that can be sometimes confusing if not having this in mind.

For preparing shadow around the target we could rotate the newly imported panels by selecting it and use menu Operations‣Transformation‣Rotation. We select Axis by clicking OZ. Required angle of rotation is -40 degrees with Preview see that the panels combine quite nicely.

../_images/geom_13.png

However, this means that we will have twice as much CAD geometry to mesh. Therefore, we restrict ourselves just to one blanket segment in CAD and replicate meshes as needed in Mesh module once we have them.

To complete this tutorial we just rename imported surface model to PANELS and save the study somewhere for meshing.