Difference in Circular and Normal Symmetry

Hi guys,

I have a cylinder type of model (similar to a pipeline). I have cut into a 1/12th portion of the circular along the centre line of the cylinder.

When I had my training on Simulation, I have been told to use circular symmetry on this kind of cylindrical shape problem.

However, recently i found out that we can apply normal symmetry too on both faces.

Can I know what are the differences between circular and normal symmetry and why am I allow to use normal symmetry (in my example)?

I can post a picture of my example if needed.

Further more, I realised for the same problem, normal symmetry used 6 minutes to solve, but circular symmetry use up to more than 2 hours (maybe more, and maybe crash the STAR Solver).

Why?

Thanks.

SolidworksSimulation