Rotational periodicity on tetra meshes with ICEM
 

Hi, I'm working with ICEM CFD 10.0 and I'd like to know how to define a rotational periodic boundary for a tetra mesh used on a turbomachimery simulation. Is it done by creating nodes on the surfaces and relating them as periodics? What happens if the surfaces have a complicated geometry and aren't defined with four corners as when blocks are used?

Can anybody help me? thanks