The main conclusions in relation to the numerical aspects can be summarized as follows: In general stable solutions for higher Reynolds numbers can only be reached with non-centred differences for the approximation of the convective terms and with smoothing techniques (compound iteration). Furthermore this fact is true for explicit schemes and implicit schemes as well (integer or fractional time step methods). Explicit schemes on the verge of instability are competitive with implicit schemes. In the higher range of Reynolds numbers and with large time steps splitting methods seem very inaccurate. Obviously in such cases a great truncation error is involved and only qualitative global accuracy may be claimed.