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# Example of usage mesh 1D and 0D algorithms and hypothesis

## Example of usage mesh 1D and 0D algorithms and hypothesis

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

This exercise illustrates the use of SMESH SALOME 1D and 0D algorithms and hypothesis and functionalities for meshing of the prism shape. Note that choice of mesh strongly depends on problem under investigation.

### Geometry

The sequence of actions is as follows:
• Launch SALOME.
• Create a new study.
• Launch GEOM module.
• Tap in Object Browser from popup menu - Refresh
• Explode into basic elements: (menu New Entity/Explode)
Explode Prism_1 into Edges.
Explode Prism_1 into Vertices.

### Construction and modification of the mesh

Launch SMESH module.
• Creation of Mesh_1 : (menu Mesh/Create Mesh)
Geometry: Prism_1
1D algorithm: Wire Discretization
1D hypothesis: Local length =50
Apply and Close
• Compute Mesh_1
• Select Mesh_1 in VTK viewer – popup – Numbering/Display nodes
• Controls/Edge Controls/Length
Local length hypothesis creates 1D edges with approximately equal length depending on the length of geometrical edges to be meshed. For short geometrical edges one 1D edge will be created with smaller length.

• Edit Mesh_1 : (menu Mesh/Edit Mesh/Sub-mesh)
0D algorithm: Segments around Vertex
0D hypothesis: Length Near Vertex = 25
Apply and Close

• Compute Mesh_1
Length Near Vertex hypothesis permits to reduce length of 1D edges near vertices.

• Creation of SubMesh_1 : (menu Mesh/Create Sub-mesh)
Geometry : Edge_1 (vertical edge)
1D algorithm: Wire Discretization
1D hypothesis: Nb. Segments =1. Equidistant distribution
Apply and Close

• Compute Mesh_1
Number segments hypothesis strictly define number of 1D edges independently from length of geometrical edges.

• Submesh permits to mesh some region of interest in other way than the whole mesh.
Edit Mesh_1 : (menu Mesh/Edit Mesh/Sub-mesh)
Add. 1D hypothesis: Propagation of 1D Hyp. on opposite edges
Apply and Close
• Compute Mesh_1
Propagation of 1D Hyp. on opposite edges additional 1D hypothesis permits to keep the same number of 1D edges on all parallel geometrical edges. This is very important for creation of hexahedral meshes.

• Edit hypothesis Nb. Segments_1: (object browser – popup Edit hypothesis)
Number segments =4. Scale distribution
Scale factor 3
OK

• Compute Mesh_1
Using of Scale distribution for Number segments hypothesis creates 1D edges with different length and permits to make finer mesh in the area of interest.

• Creation of SubMesh_2 : (menu Mesh/Create Sub-mesh)
Geometry : Edge_12 (curved edge)
1D algorithm: Wire Discretisation
1D hypothesis: Deflection 1D
Deflection = 2
OK, Apply and Close

• Compute Mesh_1
Deflection 1D hypothesis allows to mesh curved edges.

• Edit Mesh_1 : (menu Mesh/Edit Mesh/Sub-mesh)
Add. 1D hypothesis: Propagation of 1D Hyp.
On opposite edges
Apply and Close

• Compute Mesh_1

• Delete node : (menu Modification/Remove/ Nodes)
Select node ID = 2
Apply and Close
Note that elements containing removed nodes are also deleted.

• Delete elements: (menu Modification/Remove/ Elements)
Select edges ID = 3, 53
Apply and Close
Note that nodes of removed elements remain in mesh.

X=4, Y=35, Z=103
Apply and Close

Select nodes 10 and 11
Apply and Close

Select corner nodes 11 and 2
Select middle node 50
Apply and Close