[hesoyam]

Background: I am running a simulation where a propeller blade is rotating in within a static fluid domain. I am using a quadrant for both my domains. The green portion is the blade domain where the blade is at and the grey portion is the fluid domain.

I am trying to set periodic conditions for both domains but upon initializing, this error keeps appearing. I know this will, in the end, affect my results but I just can't seem to fix it. I suspect it is something wrong with my mesh but I have been going nowhere with it too. I am using the meshing software 'mesh' within Ansys and tried many ways but still, this error keeps appearing. I have also tried reconstructing the geometry but also didn't help

error: non-conformal periodic interface f.p with empty intersection. this is likely due to incorrect specification of periodic offset values. please check the offset values specified and recreate the interface.
(f.p fluid periodic)

[vinerm]

The model does not appear to be a quadrant. I suppose you want to apply rotational periodicity. For rotational periodicity to work, the axis definition for the cell zone must be correct. Secondly, mesh on both of the periodic faces must be same. Default axis in Fluent is (0 0 1) and the origin is (0 0 0). If either or both of these are not as per your case, then you need to change those before creating a periodic boundary. These changes are to be made in the cell zone conditions.

[hesoyam]

@vinerm

Thanks for the quick reply!

1) attached is the quadrant just for the blade domain
2) I have applied matching mesh for the sides I want to have periodic
3) According to my scale shouldn't it be the default.

Thanks in advance!

[vinerm]

It appears to be correct. What commands do you use to create periodic condition?

[hesoyam]

I did not use the console, instead, I changed the type in the boundary conditions and manually changed to an interface. After that, I went to the mesh interface and manually create a periodic boundary condition.

The console didn't work for me as it prompts an error stating it failed to make zones periodic

[vinerm]

If Fluent is unable to create rotational periodic boundary condition using commands then that means either the mesh on the periodic boundaries is not matching or the angle is different for the matching boundaries along the axis. When you use commands and it falls, Fluent will show a reason as well. What reason does it show?

[hesoyam]

Thanks for the reply!

It shows,
Error: Failed to make zones periodic. Error Object: #f

[vinerm]

You have to ensure that the meshes at both the surfaces are same. If that's not the case, then you can create a mesh interface and while creating interface, you can define it as translational periodic.

[hesoyam]

During my meshing, I applied match control for the faces I want to make periodic. Also, my blade domain is rotating I set it as rotational periodic

[vinerm]

If the mesh is same, then Fluent is unable to determine the separation automatically. You can set it manually while creating the translational periodic boundary. Fluent asks for automatic creation. You can answer as no and then provide your own vector. Do note that (0 0 -1) is different from (0 0 1) for translational periodic. If the axis is (0 0 1) and you choose inlet first, then vector must be provided as (0 0 1) but not as a unit vector. If the gap is 5 cm, provide it as (0 0 0.05).

[hesoyam]

Sorry, but I don't quite get it. Plus my periodic condition is a rotating periodic. I can't seem to obtain an accurate offset angle. When i auto-compute fluent either prompts that it is unable to determine an angle or gives a number that isn't divisible equally with 360deg. Furthermore, even if i hard set it as 90 or -90 the error in the first post will appear.

Thanks

[vinerm]

I apologized, I mixed your post with someone else's. If you give an angle, then you Fluent will take that and do the calculation accordingly. If the angle really is 90, then you can proceed further. If it is not, then provide correct angle as input.

[hesoyam]

I tried both entering a figure and allowing fluent to auto compute but the error on the first post kept on appearing

[vinerm]

The image in the first post shows error that appears when you try to create mesh interface with periodic boundary option. That is not when you try to create periodic boundary without the mesh interface.

[hesoyam]

I am sorry i dont quite get what you mean. I am kinda new to fluent

[vinerm]

There are two ways to create a periodic bc; direct method by using commands and it requires mesh to be exactly same on both faces, within a certain tolerance, and second is by use of mesh interface. The error you showed in the first image is from the second method. Did you try the first method because that is preferable?

[hesoyam]

Hey sorry for any inconvenince.

I did try the first method of using the console anf typing the command. However it prompts the

Warning: Number of elements does not match between zone 12 and 13.
Error: Failed to make zones periodic.
Error Object: #f

I dont get it as i have applied matching during meshing for the zones i wanted to make periodic.

[vinerm]

At least now the issue is known. So, either you can go back and generate mesh where meshes match with each other or use mesh interface in Fluent to create periodic boundary. For that, you have to change both periodic boundaries to interface type under Boundary Conditions and then use Mesh Interfaces to create a rotational periodic interface.

[hesoyam]

Honestly, i am at my wit's end. I have done what you recommended a few times. i have tried using a new model. Re-meshing everything from scratch. varying the two methods in periodic boundary creation. All these and still the same problem.

I sometimes get this too. Warning: Periodic angle of -14.036247 does not divide 360 (deg) evenly.

[vinerm]

This implies your geometric model is created incorrect. The angle of periodic domain should be such that you get an integer when you divide 360 by the angle of the domain. Only then you could have a physically realistic system.