[panda60]

Dear all.
I want to creat cyclic boundary using a pair of patches in lateral.
I want to do channel flow simulation, my wind comes from left.
So I think my cyclic boundary should be translational, not rotational.
But I don't know the meaning of separationVector , how should I set this vector when generating cyclic boundary . who can give me a explanation, Thanks.

patches
(
{
// Name of new patch
name CYCLIC;
// Type of new patch
dictionary
{
type cyclic;
transform translational;
separationVector (0 1 0);
}
constructFrom patches;
patches (CYCLIC_LEFT CYCLIC_RIGHT);
}
);

[sinatahmooresi]

Originally Posted by panda60

Dear all.
I want to creat cyclic boundary using a pair of patches in lateral.
I want to do channel flow simulation, my wind comes from left.
So I think my cyclic boundary should be translational, not rotational.
But I don't know the meaning of separationVector , how should I set this vector when generating cyclic boundary . who can give me a explanation, Thanks.

patches
(
{
// Name of new patch
name CYCLIC;
// Type of new patch
dictionary
{
type cyclic;
transform translational;
separationVector (0 1 0);
}
constructFrom patches;
patches (CYCLIC_LEFT CYCLIC_RIGHT);
}
);

Hello Jiang,

I have the same problem in finding the definition of separationVector. Did you find out?


Thanks,

Sina

[Alczem]

Hello,


I believe it is the vector from cyclic patch to the other patch. So for instance, if you had two cyclic patches behaving as an inlet and outlet for a 1 meter long channel simulation in the X direction, you should type separationVector (1 0 0) and separationVector (-1 0 0) for the inlet and outlet.


Hope you figure it out

[sinatahmooresi]

Hello Alczem,


Thank you for your response. I have a question regarding the "translational" option in the cyclic boundary condition in OpenFOAM. Specifically, I am wondering why it is necessary to use this option. When I apply the "cyclic" boundary condition without "translational", I get the same results as when I use it. My goal is to model a pipe flow with fully developed turbulence at the end of the pipe, which will then be released as a jet flow into a receiving domain such as a tank. To achieve this, I am using cyclic boundary conditions at the inlet and outlet of the pipe. However, my results show a fully developed laminar condition, with the maximum center value twice the inlet average. I am unsure why this is happening and would appreciate any insight you could offer.


Thank you,
Sina

[Alczem]

Hey,


I don't use this condition too often, so I cannot point you in the right direction easily. Can you share your case? It might help someone diagnose the issue


Off the top of my mind, did you make sure your two cyclic faces are identical (same number of faces, same geometry etc)? The cyclic type works only with conformal patches (identical patches, only at different locations). If it is not the case, you might want to look into the ACMI patches I think.

[sinatahmooresi]

Hello Alczem,


I'de be happy to share the case. I should mention that I made some changes to my solver (pimpleFoam) to be non-dimensional. Thus, the viscosity is changed and the every filed value is turned to unity at the inlet. How can I share the case here. looks like it is not easy to upload files larger than 100KB.



Sina