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# Extrusion along Path and meshing example

## Extrusion along Path and meshing example

This sample is known to work on the latest SALOME release.
The compatibility with previous versions of SALOME is not guaranteed, though the sample can work on old versions also.

### Objective

The purpose is to produce a prismatic meshing on a curved geometry.

This tutorial is a part of the EDF internal training course; it does not describe a real use case.

### Geometry

• Launch SALOME.

• Create a new study.

• Launch GEOM module.

 Launch the sketcher (Menu New Entity/Basic/2D Sketch) to construct the axis of the tube: Attention: Don not forget to validate each segment except for the last one using «Apply» Point of origin: X=0, Y=0 1st vertical: Segment / Point / X=0 Y=200 1st arc of circle: Arc / Direction / Tangent / Radius 100 Angle 90 Horizontal: Segment / Direction / Tangent / Length 200 2nd arc of circle: Arc / Direction / Tangent  / Radius -100 Angle 90 2nd vertical : Segment / Direction / Tangent / Length 200 Validate the sketch: Sketch Validation Sketch_1 appears in the object browser.   Construct the Base: The circle can be by a point and a vector or by three points. The first solution will be used. Construct from the origin using the point constructor: The vector defines the normal to the plane containing the circle. The normal can be the 1st vertical: Select Sketch_1 in the data tree and click New_Entity > Explode. Select edges as the type of sub-shapes, click  Select Sub Shapes and select in the Open Cascade viewer the 1st vertical. Validate with Apply and Close, Edge_1 appears in the data tree as sub-shape of Sketch_1. Now it is possible to construct the base circles. Call the circle constructor (New Entity / Basic / Circle) The origin of coordinate system O will be the centre and Edge_1 as vector. Construct 2 circles with radius 20 and 30.   Then it is necessary to construct the base itself. Using New Entity > Build > Face, construct the geometrical base by selecting 2 circles as arguments (multiple selection is carried out by locking ctrl in the object browser or shift in the viewer). Face_1 is created. Show the Face_1 in "Shading" mode. Now this base should be extruded along the previously created path. Explode Sketch_1 into edges, Edge_i (i=2,…,6) are created (Do not select Select sub shapes) For each Edge_i, from 6 to 2, Select the tool Extrusion along a path by clicking on the icon So the Base object is Face_(i_1) and the Path Object is Edge_i. This forms a geometry Pipe_(i_1). Explode Pipe_(i_1) with activated option Select Subshape toselect the face, which will be the base for the next extrusion. In this way we have constructed the 5 geometries.  Now they should be grouped in one solid. For this, use the tool Compound via the menu New Entity > Build > Compound. To perform multiple selection lock Ctrl key and select 5 objects from previous step in the object browser. The object Compound_1 is created.  The compound is just an assembly, which means that there are two faces instead of one at the connections of objects. This might hinder some meshing algorithms. So, these faces should be glued.  Select the tool Glue Faces in the menu Repair, leave the default tolerance value and give the name « Tube » to the geometry. Use the tool Measures > What is to see the differences between the objects Tube and Compound_1.  Now explode the Tube into faces and select only 6 faces corresponding to 6 sections (use shift key for selection in the viewer).  The geometry Tube is now ready for meshing.

### Mesh

Construction of the Tetrahedral mesh, non-repetitive mesh.

Activate module SMESH.

The algorithm of tetrahedrization works very simply:

Click Create Mesh Select the geometry Tube Click Assign a set of hypothesis > Automatic Tetrahedralization

SALOME asks to define Max. Length parameters. Click Cancel.

Select 1D tab, add "Automatic Length hypothesis" input the length parameter: Choose something like 0.5. (the finer the mesh is closer to 1)

Now it is possible to validate by OK.

When the hypotheses and algorithms are correctly defined, click Mesh_1 -> Compute to compute the mesh.

A dialog box informs us that a tetrahedral mesh has been created.

### Construction of the repetitive mesh

Click Create Mesh.

Select the geometry Tube.

To apply the repetitive mesh, select the algorithm 3D extrusion in the tab 3D, the algorithm Quadrangle in the tab 2D and define 1D algorithm. We'll use Wire Discretisation with Number of segments = 13 hypothesis (by clicking Create Hypothesis).

Validate by Ok.

Mesh_2 appears in the data tree.

Do not click Compute, at this level, sub-meshes should be created: the base of the tube will be meshed with triangles and this mesh will be projected on each intermediate face. These meshes will be sub-meshes of Mesh_2.

First of all, we'll mesh the base with triangles:

Click Mesh > Create Sub-Mesh. Select Mesh_2 in Mesh and the base (in our case Face_21) in Geometry or in the viewer. The Triangle(Mefisto) algorithm with maximum area = 10000 hypothesis will be selected.

Validate by Ok.

SubMesh_1 appears in the data tree as a sub-element of Mesh_2.

Then this mesh is projected on all other faces:

For each projected face, repeat the following steps:

Click Mesh > Create Sub-Mesh. Select Mesh_2 in Mesh and the face on which the mesh will be projected in Geometry. Select the algorithm Projection 2D with Source Face hypothesis. In this hypothesis, select only the base (in our case Face_21) in Face. Give the name to this hypothesis to easily find it when you repeat the operation.

Validate by Ok.

Check that 6 sub-meshes are defined. It is possible to compute the mesh: Mesh_2 > Compute

A dialog box informs us that mesh with prisms has been constructed.