I'm trying to solve 2D Euler equations in axisymmetric formulation with finite-difference WENO scheme. I found some info on high-order boundary conditions for plane formulation (in this thesis, for example: 1), but couldn't find info on axisymmetrical case.
What is the correct way to implement symmetry condition at the axis $r=0$? Should we use ghost cells with $r<0$ and how to do so? Should the axis go through cell centers or in between the centers?