Publisher Summary The techniques developed in this chapter are applicable to problems where there is no obvious dominant flow direction. Also viscous–inviscid interaction is usually present, so that a separate calculation of wall regions and inviscid flow regions is not possible. Moreover, regions of massive separation are usually present with the possibility of flow unsteadiness and turbulence. The chapter reviews the numerical aspects of the discrete solutions of reynolds-averaged Navier–Stokes equations. The various performances of the techniques considered are discussed. However, the literature indicates that discussion about the performance of the various techniques is rather inhomogeneous. With regard to the choice of the formulation, it appears that methods which depart from the primitive formulation have not been investigated in general coordinates. Most of the numerical methods discussed lead to a compact stencil for the discrete momentum equations. Owing to the fact that more accurate discrete schemes should involve non-compact stencils, the convergence and stability of the resulting solvers is not strictly assured. To circumvent potential problems that could arise with these alternative discretization schemes, development and use of appropriate solvers should be considered.