This study presents findings from numerical simulations at Mach unity and compares them with experimental results under identical conditions. The flow from a converging nozzle is exhausted into an enlarged duct with a 25 mm diameter, whereas the nozzle’s inlet and exit diameters are 30 mm and 10 mm, respectively. The area ratio is 6.25. The duct length-to-diameter ratio was varied from 6 to 1. The experiments were conducted with five rectangular ribs spaced 25 mm apart. The aspect ratio of the rib was 3:1, 3:2, and 3:3. Simulations, as well as the experimental results, show that for the rib aspect ratio, there is a decrease in the base pressure.

In contrast, when the rib aspect ratio is 3:3, there is a considerable rise in the base pressure. Hence, these two ribs, with an aspect ratio of 3:1, can be used for a combustion chamber application. However, if the application is for external ballistics, then a 3:3 rib is the best option.