Effect of aspect ratio of elliptical inlet shape on performance of subsonic diffusing S-duct

The aerodynamic characteristics of S-ducts with various inlet shapes were analyzed using a commercial computational fluid dynamics tool. This study aimed to investigate the influence of the aspect ratio of inlet geometry for an RAE M 2129 S-duct. The computational results were validated using experimental data from the Aircraft Research Association. The performance of the S-duct was influenced by the location of the counter-rotating vortex on the engine face. When the center of the vortex was near the starboard side, the performance was poor. By contrast, performance increased as the counter-rotating vortex moved away from the starboard side. The center of the counter- rotating vortex of the upper half semicircular S-duct was far from the starboard side, whereas that of the lower half semicircular Sduct was near the starboard side. In conclusion, S-ducts with upper half semicircular shape had better performance than those with other inlet shapes. The AR(0.75,0) case delivered the best performance, whereas the AR(1,1) case exhibited the worst