Symmetryplanes

Kjetil W

Hi. I have a problem with a flow throug a system that is symmetric. It starts as a regular piping. At the middle of the system the flow divides into two symmetrical ducts before it returns into one piping at the end. I have defined a symmetry boundary condition to the planes before and after the part where the piping is devided, but this gives me an error when i start the solver:

" The symmetry boundary condition requires that the boundary patch mesh faces form a plane or axis. However, face set 5 in the symmetry boundary batch Symmetry is not in a strict plane, which means that at least one of its faces is not parallel to the others. "

One of the suggestions i get is that I should change the "vector parallel tolerance". But I dont understand why i should do this since the two symmetryplanes are parallell. How will the vector parallell tolerance affect results?