Numerical Simulation of Suddenly Expanded Flow from Converging Nozzle at Sonic Mach Number

Abstract

Low pressure created at the blunt base results in a substantial increase in the base drag. Controlling the base drag is required by regulating the base pressure. This study presents a turbulent numerical analysis of suddenly expanded flow in a 22 mm suddenly expanded duct with a converging nozzle which operates at sonic Mach number. A rib is placed circumferentially along the inner duct diameter. The rib is located at a different position of diameter duct namely 1D, 2D, 3D, and 4D. The height of the rib is increased from 1 to 4 mm, and the width is maintained at 3 mm throughout the study. The nozzle pressure ratio of the flow is ranging from 1.5 to 5. The numerical analysis carried out is also compared with the duct without rib. The results obtained reveal that the rib changed the flow field and causes variations in base pressure. The rib at the 2D location is found to be the base pressure controller at a moderate level. While 1D reduces the pressure, but the ribs placed at 3D/4D results in a significant increase in the base pressure level for all nozzle pressure ratios of the present study. The pressure variations and velocity field are also studied using simulation results, and they show that these parameters are influenced mainly with the use of rib of a particular location and the height of the rib.