Effect of Inlet Boundary Layer Suction on Flow Distortion in Subsonic Diffusing S-Duct

Abstract

The effects of the boundary layer suction (BLS) near the S-duct inlet on the flow distortion of the S-duct were analyzed using a commercial computational fluid dynamics tool. The purpose of this study was to investigate the effect of shape factors on the location and length of the BLS for the RAE M 2129 S-duct with the inlet shape AR (0.75,0). The performance of the S-duct is influenced by the boundary layer thickness for duct flow and the counter-rotating vortex position on the engine face. All of the cases upon applying BLS were confirmed as having a different boundary layer thickness and the counter-rotating vortex at the engine face was confirmed. The PS (0,0.1) case has the thinnest boundary layer and the counter-rotating vortex is the farthest from the starboard side, while the PS (0.06,0.08) case has the thickest boundary layer and the counter-rotating vortex is located near the starboard side. In conclusion, it was confirmed that BLS has a significant influence on the flow distortion for the applied position compared to the applied length. Additionally, the PS (0,0.1) case applied near duct inlet showed the least flow distortion, and the PS (0.06,0.08) case located near the cowl lip showed the largest flow distortion.