Flow around a cylinder / Mesh with an inner wall

[Aurélien J]

Hello,

Related to my previous post, I am willing to carry out 2D simulations of flow-induced vibration of cylinders with different cross sections. I am quite new in Code_Saturne.

I have started producing my own meshes using Salome, but the meshes I made produce a boundary condition error when I start the computation, even when I don't use the ALE mesh movement. The preprocessing seems to run normally. I know it is a mesh of poor quality but I would first like to have a computation running properly.

Code: Select all

First face with boundary condition definition error
  (out of 1)
  has boundary condition type 0, center (0.4, 0.9, 2)

cs_boundary_conditions.c:429: Fatal error.

I tried without the square in the middle, so basically a 2D mesh where nothing happens, and there the computation runs without any error. So it seems that the problem lies in the boundary region of the square (same problem with a circle).

I also tried to modify the orientation of the faces of that inner boundary region but it failed as well.

I used Code_Saturne 2.0.2. I did also one computation with Code_Saturne 3.0.1 and it wasn't successful either.

Attached are the xml file, the mesh, the preprocessor listing and the log file with the error. I would be grateful for ideas about how I can avoid this error.

Regards,
Aurélien

[Yvan Fournier]

Hello,

Did you check the error visualization output, as indicated in the "listing" ? (it is the ERROR.ENSIGHT output). Compare it with the groups you obtain when running "check mesh" (in PREPROCESSOR.case, if you are using ParaView, do not forget to use the "extract blocs" filter to see the differnt parts).

When you do that, you'll see that one of the faces on your mesh does not have the correct group (you could also have noticed in the "listpre" file that you have 200 cells, but only 399 faces belonging to sides, instead of 200*2=400).

Once you visualize where the error occurs, you can fix your mesh.

Regards,

Yvan

[Jacques Fontaine]

Hello,

You can open the error.CASE with SALOME or ParaView to show the faces without BCs.
It's not a problem of orientation, I think you forgot to give a color to the extruded wall.
You can check the colors by running Code_Saturne in mesh quality mode (do not forget to apply "Extract Block" filter for the visu in ParaView).

You can also impose your BCs with geometrical criteria (symmetry: z > 1.999 or z < 0.0001).

Regards,

Edit: owned by Yvan

[Aurélien J]

Thanks a lot for your answers, I will try to do this.

Regards
Aurélien

[Aurélien J]

Hello,

Thanks for your indications, I indeed managed to correct my mesh and to run this sample simulation. I am slowly getting acquainted with Code_Saturne.

Moving on to the next problem... it may have more to do with Salome than with Code_Saturne but you could maybe have, again, some good advice.

I have created the following mesh using Salome :

with these groups :

0513meshgroups.jpeg

(16.45 KiB) Not downloaded yet

The preprocessor finds another group ("no_group"):

Code: Select all

Definition of face and cell families
------------------------------------

  Family 1
         Group "All_Faces_extruded"
  Number of cells          :     3470
  Family 2
         Group "Bottom_extruded"
  Number of boundary faces :       90
  Family 3
         Group "Cercle_extruded"
  Number of boundary faces :       62
  Family 4
         Group "Inlet_extruded"
  Number of boundary faces :       35
  Family 5
         Group "Outlet_extruded"
  Number of boundary faces :       35
  Family 6
         Group "Side1"
         Group "Sides"
  Number of boundary faces :     3470
  Family 7
         Group "Side2"
         Group "Sides"
  Number of boundary faces :     3470
  Family 8
         Group "Top_extruded"
  Number of boundary faces :       90
  Family 8
         Default family
         (no group)
  Number of internal faces :     6570
  Number of boundary faces :      428

which will end up making problems : (lines 654 to 656 of listing file)

Code: Select all

First face with boundary condition definition error
  (out of 428)
  has boundary condition type 0, center (1.5, -1.03125, 0.5)

Opening ERROR.case and /check_mesh/postprocessing/BOUNDARY_GROUPS.case with Paraview, I find out indeed that the origin of the error lies in that "no_group" boundary region. According to the listing file, I have not defined any BC for that region, but the solver expects one.

Therefrom my question : where did this boudary region possibly come from and how can I get rid of it?

I would be pleased to read your explanations.
This time I have used Code_Saturne 3.0.1.

Regards

[Yvan Fournier]

Hello,

Now that you have visualized where the face with no group is located, you know what to look for when checking your mesh under SALOME.

I do not know whether the face missing from the group is due to a user error or a bug in SALOME (depending on whether you defined the groups using a filter or a mouse selection), but in any case, you can edit the mesh under SALOME to add that face to to group to which it belongs. This is not a Code_Saturne issue, but a user/SALOME issue. Code_Saturne just helps you visually check your input so that you can fix it more easily.

So now good luck fixing your mesh.

Regards,

Yvan

[Aurélien J]

OK, thanks.