one face turn to be two in pre
 

I am simulating the flow field of a large room. There are several pipes in the room. Air flows from the large room to the outer environment through pipes.

I try to start with an easy model.
First i model the room and then i direct model one pipe in the room through UG.

When meshing, I creat two material bodies, one for the pipe, and the other for the big room.

And i named the the inlet face of the pipe which connects the big room as IN.

But when i load the mesh in the CFX-pre, I found the CFX named the IN as
IN-a,IN-b.

Why will that happen?
Is it OK?

This is probably because the IN surface is shared by two domains (materials) here - pipe and room. Hence a and b sides belong to the two domains meeting at your surface.

As long as both are same materials, ie air, you should be fine.

OJ