Upstream rocket centreline singularity treatment

Bigarella

Hy!

I'm an MSc student and I'm currently working with a 3-D Finite Difference Method for general curvilinear coordinate systems. Its application is mainly supersonic flow simulations about rocket-like configurations.In order to generate a 3-D mesh for the rockets, the approach is to generate a 2-D plane and rotate it about the symmetry axis. My problem is with the singularity of the coordinate trasnformation that appears in this upstream centreline with this rotation. Does anybody here happen to know how to deal with boundary conditions and, foremost, metrics treatment in this singularity line?

Thanks in advance.