Create Hypotheses in Salome 3.2.1 ?

Hi everybody!

Just found CAELinux and you did a great job!

I'm trying to learn Salome using the piston tutorial included in CaelinuxBeta3 by I can't overcome the hypotheses step: the \"create hypotheses\" menu command or icon doesn't seem to be there any more (in the tutorial screenshot Salome versionis 2.2.2 ...).

I realized I can \"create mesh\". This command enables the hypotheses creation but:
- I can't set the parameters that are written in the tutorial;
- I always get thi (kind of) error: \"mismatch of submesh dimension and hypotheses\".


Any advice to walk over this step?

Thanks a lot

Shock99er

I'm brand new to CEALinux too & am having similar problems.

I have solved the hypotheses problem (I think!).

Follow the tutorial .PDF up to the 'Select menu hypotheses' bit. Instead, click on the Tree view 'Piston.stp_1' under 'Geometry' the select Menu Mesh -> Create Mesh' A 'Create Mesh' box will appear with 'Mesh_1' in the Name slot and 'Piston.stp_1' in the 'Geometry' box. Below them, there is a set of tabs marked '3D', '2D' and '1D'. The '3D' tab will be highlighted. Use the dropdown button on the Algorithm box & select 'Tetrahedron (Netgen)'. The first button to the right of the 'Hypothesis' will light up. Click on it & 'Max Element Volume' will appear. Click on that & a 'Hypothesis Construction' box will appear where you can enter the value (100 IIRC) & click OK. Now click on the '2D' tab & do the same for 'Triangle (Mefisto)' and 'Length from edges' then the '1D' tab for 'Wire Discretisation' and 'Average Length','5' After that, click OK to close the Create mesh' box. You should then have a 'Mesh' element in the tree view which, when expanded out, looks about the same as the tutorial screenshot.

HOWEVER, when I select Mesh_1 and do Menu Mesh -> Compute, I get a short wait and a 'Warning' message box which says, \"Mesh computation failed\" but gives no indication as to why or how I can find out & fix it

Now what do I do? Anyone?

Hello,

sorry for the tutorial, it has not been updated for Salome 3.2 yet. A good starting point for mesh generation in Salome 3.2 is to use the \"automatic tetrahedralization\" preset in the \"Create Mesh\" dialog (appears at the bottom of the dialog). This preset creates a set of 1-2-3D hypotheses based on \"Automatic size\", \"Triangle (Mefisto)\" & \"Tetrahedra (Netgen)\". Thanks to the use of \"Automatic size\" as a 1D hypothesis, you do not need to enter a characteristic element size anymore, but you can simply adjust the mesh density with a cursor between 0 (coarse) and 1 (fine) as you would do it in Ansys Workbench for example.
As a rule of thumb, I would recommend that you always start with a very coarse mesh (cursor on 0) before you try to refine it (very fine mesh can take hours to be generated...).

Using this procedure should give you good results in most cases without complex parameters. If this procedure fails, first try to refine the mesh progressivly, and if necessary, select the 3D hypothesis called \"Netgen 1D-2D-3D\" to use the Netgen lib for the complete mesh generation (you should adjust the parameters manually in this case). In general, the netgen 1-2-3D algo is more robust than Automatic length-Mefisto-Netgen(tetra) but it also tends to generate finer meshes around corners and takes much more time to generate the mesh.

I hope that my answer is sufficiently clear for you... if not, don't hesitate to ask.

PS: I will be away from office during the next week... so be patient !!

Hi Admin,

Thanks for your reply. I understand that it takes time to upgrade tutorials when new software versions become available and CAELinux is, after all, still in Beta.

The Automated method you suggested does indeed allow me to successfully compute the mesh. Excellent

So now I can progress to the next step of the tutorial....

Hi Admin! Thanks for your suggestions. I managed to walk over that problem.
Approaching the piston tutorial now

Thanks again and keep you great job!

Shock99er!