In my application I have created a small rectangular face inside a bigger one with its edges defined with interior boundary condition. However when I read the mesh file in Fluent6 it gives an error msg saying that the edges of the inner face are only one sided threads. How can I make the edges of inner face two-sided? I need the interior boundary condition on the inner edges. thanks Kshitij

The "only one adjacent cell thread" warning comes because fluent only sees a mesh on one side of the edge. It has to do with how you modeled the faces. There are two possibilities here... one is that you have two triangles, one on-top of the other. Or you have a big traingle with a hole the size of the small triangle, and you have a small triangle to fill that hole, but the edges aren't connected. If the big traingle doesn't have a hole in it the shape of the small triangle, then all you have to do is use the split command (split the big triangle with the little one, making sure the connected option is turned on... this will leave you with a big traingle with a hole in it, a little triangle to fill the hole, and they will be sharing the three edges). If the big triangle does have a hole in it, then you have to manually connect the edges (in the edge commands, it's in the top row of icons second from the right... it looks like a black plug). This way the two faces are now sharing the three edges. You'll probably have to remesh, and you might have to reset your BCs.

Hope this helps, and good luck, Jason