Study on computing separating flows within a diffusion inlet S-duct

Abstract

A three-dimensional implicit full Navier-Stokes (FNS) analysis and a three-dimensional reduced Navier-Stokes (RNS) initial value space marching solution technique have been applied to a class of separated flow problems within a diffusing S-duct configuration characterized as vortex-liftof f. Both the FNS and the RNS solution technique were able to capture the overall flow physics of vortex liftoff, and gave remarkably similar results which agreed reasonably well with the experimental performance data. However, the FNS and RNS also consistently predicted separation further downstream in the M2129 inlet S-duct than was indicated by experimental data. The separated region associated with vortex liftoff in M2129 inlet S-duct increased in size as the inlet mass flow increased, although the radial extent of the reverse flow region remained very small. Since the reverse flow velocity was also very small, the separated flow in the M2129 S-duct might be regarded as incipient. This, along with the fact that the RNS analysis was able to capture the topology of vortex liftoff, indicates that the parabolized form of the Navier-Stokes equations are appropriate for separated flows represented by the M2129 inlet S-duct.