Abstract: Three-dimension, compressible, internal flow solution obtained using a modifiedBeam-Warming implicit factorization scheme is presented. Steady-state solution is obtained by solving numerically the full Navier-Stokes equations from given initial conditions until the time-dependent terms become negligible. The configuration considered is a rectangular cross-section, S-shaped centreline diffuser duct with an exit/inlet area ratio of 2.25. TheMach number at the duct entrance is 0.9 with a Raynolds number of 5.82×10⁵. Two regions of separated flow exist within the diffuser. The detail flow field especially the developement process of secondary velocity patterns in transverse plane are pressented. Comparing with the results ofRef.[1]. they have a good agreement. The secondary velocity patterns are more reasonable.

Key words: internal flow, numerical computation, separation, secondary vortex, diffuser