Interface
 

1.

I assembled components A(innermost), B(inner) and C(outer)
I then extracted the internal volume which I imported as one part.
I split this part by non- contiguous to form part surfaces A1, B1 and C1 corresponding to my initial components
I then assigned the part to region with this part surfaces becoming boundaries A2, B2 and C2 for my region.

I wish to know, to properly demarcate the boundaries, do I still need to convert A2, B2 to interfaces

Or do I need to create interfaces between them

Is there the need to also create an interface between C2 and B2?

A2 and B2 are obstructions in the flow. Should their interface type be baffle?

C2 is the fluid domain, what interface type should i form between this and B2

2.
I also wanted to create a fully developed periodic interface between my inlet boundary and outlet,
In the axis properties which is needed for periodic transformation, I inputed my direction but I dont really understand what should be the origin.

Is the origin specified at my inlet boundary or the outlet or the origin of the xyz laboratory plane?

3
Is there the need to intersect the periodic boundaries for fully developed interface?
After I used the origin of the xyz laboratory plane, and tried to intersect, the output warning was no boundaries intersected.

I need your help please.

:confused:

Why did you import as one part, why did not import as a region considering one boundry for one face?

1. You need to create interfaces between all parts you want energy, momentum or mass to be transferred.
Usually interfaces are in-place (fluid-fluid) or contact (fluid-solid). A baffle doesn't allow any fluid to pass through the interface and are mostly used to model thin objects like sheets, heat shields etc.
But when your flow is isothermal, you don't need to simulate your obstructions in the flow. Just reject this parts and have some wall boundaries there. A wall is an obstacle for the flow, no matter if the solid exists in your domain or not.

2. You only need to specify the axis when your interfaces are not parallel. E.g. you want to simulate a periodic wedge, but then it's pretty clear where your origin should be. When it's just a straight tube, you should be able to set the periodic transformation to "translational" and forget about the axis.

3. You usually don't need to intersect any boundaries. An intersect just marks the edges where one boundary cuts the other one. That might be used to split boundaries, but it CAN NEVER do anything useful when the boundaries doesn't touch each other.