[andrearimo]

i'm trying to build a mesh for a 2D case similar to 2 big reservoir connected by a pipe.

i'm doing this defining 3 rectangles, 2 big tanks, and one small rectangle connecting them.
i meshed them in such way that the nodes fo the small rectangle fall exacly on the nodes of the the 2 big tanks.
the problem is that if i try to merge the patches at the interface it gives me hundreds of severe non-orthogonality with angle = 180deg...

so my question is: is there a rule to define the normal of the 2 patches to be merged?

Thanks
Andrea