Comparison between two finite‐difference schemes for computing the flow around a cylinder

Separated flow past a circular cylinder is computed from two finite‐difference Navier–Stokes models. Stream functions are calculated using a successive‐over‐relaxation (SOR) procedure. Alternating‐direction‐implicil (ADI) and ‘upwind’ directional difference explicit (DDE) numerical schemes for solving the vorticity‐transport equation are compared. The ‘upwind’ differencing technique produces artificial viscosity which damps the wake and suppresses vortex shedding. It is shown to be unreliable and so the ADI approach is recommended.