[Persil]

Hello,

there are quite a few threads to this topic here, but I tried multiple methods already so starting a new 1 sems legit...

as you can see in the picture, I want to create to periodic boundary conditions: a) the faces on the top, b) the faces on the bottom

creating works without an error, but when exporting the mesh, following error appears:

"boundary entity ***_shadow does not contain any valid entity and is not written.
periodic boundary entity *** is not specified correctly. The two periodic entities must be link meshed and specified on the same boundary entity."

the problem is: I thought I did that already by face-linking the top and bottom before starting, splitting edges/faces and creating stuff... I even renewed the mesh-link when I splitted the volume and merged faces afterwards, because there I got the message, that mesh-links had been deleted to compute the command

I also tried keeping the bc as SYMMETRY and then changing them later in fluent to PERIODIC, but this was also not possible...

Nex thing I want to do is exporting with bc INTERFACE and then create periodic bc in fluent, but dont know if this is sufficient...

any ideas?

[flotus1]

Originally Posted by Persil

I also tried keeping the bc as SYMMETRY and then changing them later in fluent to PERIODIC, but this was also not possible...

Nex thing I want to do is exporting with bc INTERFACE and then create periodic bc in fluent, but dont know if this is sufficient...
(

"was also not possible" is a bit unspecific as an error description, but I guess that you did not find anything called "periodic" in the drop-down list.

Generally, you have two options to create periodic boundary conditions in Fluent directly. For both of them, the name or initial type of the boundaries involved are irrelevant.

1. non-conformal interface via GUI
   Set the types of the two boundaries to interface. Then you can create a periodic interface in the mesh interfaces tab in Fluent.
2. periodic boundary condition via TUI
   Enter "mesh" "modify-zones" make-periodic"
   Here you will have to specify the IDs of the boundaries involved (find them in the boundary conditions tab) and if you want a rotational or a translational periodicity.
   For this method, the meshes on both surfaces must be conformal.

[Vidyanand Kesti]

the mesh size at the both side is same?

is it rotating periodic then it should be an angle with origin

[Persil]

thx for the quick replies!

yes, I was not able to choose periodic from the drop down list...

@flotus1: Those are the 2 methods I tried and failed, because I forgot to apply them as rotating periodicity...

Now I used /grid/modify-zones/mp with checking yes as rotating

... and fluent was able to create a periodic bc out of the two interface-zones, 1 was deleted in the process and now I can get information about the new zone via right-clicking, but when I right-click on the shadow-zone the attachment is displayed. Do I have to check the grid again or how will the zones be renumbered without giving an error?

--> saving the file solves that problem

[RodriguezFatz]

Where do you right-click? In the 3d window on the mesh?

[Persil]

yes, I right-clicked in the 3D-window which displays the mesh and there on the zone, which I labeled to be the shadow-zone when I created the periodic bc... then the error was displayed, but this could be solved by just saving the file and open it again

[RodriguezFatz]

Alright, because in my file I can't click on the shadow zone...

[Persil]

yes, when I open the file again after saving, I cannot select the shadow zone, it will always be labeld as the periodic zone...

I got another question, that kind of follows up: I imported several mesh files into gambit. When I export them as 1 mesh, which will then be imported into fluent, changing the boundary condition to periodic via mesh>modify>mp is no problem...
but if create groups in gambit, arrange them via "align" and import the mesh file into fluent, not all boundary conditions can be changed to periodic... how does the group alignment disable the change of boundary conditions?

[ascedragon]

i also have problems about periodic boundary condition.. i already have a design of two steam turbine blade. can someone please help me step by step from mesh part to fluent so that i get the periodic boundary condition..... help me turbo engineer...

[Persil]

before meshing or even spliting edges and faces, you have to face-link the periodic boundaries, so that everything you do at one border will be mirrored onto the other...

but still in Gambit for me it was not possible to export periodic boundayries, I asigned them as SYMMETRY and changed them later in fluent via mesh/modify/mp to PERIDIC boundaries

[ascedragon]

thanks persil for helping me.. how can i face-link the periodic boundaries? i dont know to choose which one is the high and low boundary in my design.. i'm still amateur using CFD software..

[Persil]

I am new to cfd also, so I can only help you with things I experienced in the last weeks and well thought guesses

I don't think that it matters which 1 you choose as the top 1, as long as the vertices you select are corresponding to the surfaces

Do you use gambit for the meshing? there you face-link via face and vertex selection, where you can enable periodic and reverse (if needed)

[ascedragon]

no, i'm using ansys workbench 14.5..
ok, thanks persil.. i will try...