Finite-Difference Investigation of Axisymmetric Inviscid Separated Flows   with Infinitely-Long Cusp-Ended Stagnation Zone. Flow around a Sphere
  The classical Helmholtz problem is applied for modelling the axisymmetric inviscid cusp-ended separated flow around a sphere. Two coordinate systems are employed: polar for initial calculations and parabolic the latter being more suitable for investigation of infinitely-long stagnation zones. Scaled coordinates are introduced and difference schemes for the free-stream equation and the Bernoulli integral are devised. The separation point is not initially prescribed and is defined iteratively. A separated flow with vanishing drag coefficient is obtained. 
M.D. Todorov