Base Pressure Control with Annular Ribs

This paper presents the experimental results on the flow characteristics of a suddenly expanded flow from subsonic and sonic nozzles. The present study employs passive control in the form of a rib to investigate the base pressure for the enlarged duct. The nozzle pressure ratio (NPR) was varied from 1 to 7. The length to diameter ratio of the enlarged duct was varied from 0.5D to 6D. The aspect ratio of the rib was varied from 0.45 to 1.25. The -experimental results showed that the base pressure was strongly influenced by the aspect ratio of the rib at a given L/D ratio. For L/D = 0.5, NPR 3 was found to be critical as seen from the increasing trend in base pressure with NPR. The present study explicitly reveals that, the base pressure in a suddenly expanded axi-symmetric duct can be controlled by employing a rib of appropriate aspect ratio as a passive control device.