Virtual Origin. Axisymmetric Jet

Christine

I am trying to validate my code about an axisymmetric laminar jet, using Prandtl equations (boundary layer approximation). I am using an implicit method. My computational mesh has 7.000.000 computational points, from 0<x<20 (axial coordinate) to 0<r<15000 (radial coordinate adimensionalized with orifice radius) in non dimensional values.

The theoretical solution is given by Schlichting velocity profile in the far field. Although the numerical one seems to fit the theory well, it does not make so just in the axis, causing my virtual origin to diverge instead of converging to -0.225.

Has anyone some experience in programming this flow problem?. I think I am doing something wrong.