Impact of annular ribs in sudden expansion flow conditions to control base pressure

Abstract The experimental findings on the properties of an suddenly expanded flow from convergent nozzle is presented in this article. For suddenly expanded subsonic, sonic and underexpanded flows, the effect of passive control in the form of an annular rib on the base pressure distribution along the enlarged duct is examined. The range of the nozzle pressure ratio (NPR) was 1–7. The enlarged duct’s length-to-diameter ratio was adjusted from the base to 0.5D to 6D. The rib’s aspect ratio was adjusted between 0.45 and 1.25. The experimental findings demonstrate that, in the absence of ribs, the base pressure is highly impacted by the flow Mach number, the degree of expansion at the nozzle exit, and the length-to-diameter ratio of the enlarged duct. The base pressure of a sonic jet with NPR 4 rises as the rib aspect ratio does as well. The current study clearly shows that, in a suddenly expanded axi-symmetric duct, the base pressure can be managed passively by using a rib with the proper aspect ratio. This prevents wall pressure oscillations from rising to an unacceptably high level in subsonic and appropriately and underexpanded sonic flow.