Pressure Characteristics Exerted on Base by Underexpanded Jet of Powered-On Supersonic Vehicles

Abstract

In this study, the characteristics of the base pressure based on a powered-on supersonic vehicle and a strongly underexpanded plume jet were discussed. We investigated the case where the plume jet was “confined” at the base because the nozzle lip was absent or short. Separation points and separation angles were presented to quantitatively analyze the recirculation zone induced by the plume jet. Furthermore, a method to obtain the base pressure was proposed. Numerical analysis was conducted at freestream Mach numbers of 3, 4, and 5; jet pressure ratios of 5, 20, 35, 50, and 65; and plume specific heat ratios of 1.1, 1.2, 1.3, and 1.4. The calculated average base pressure coefficients were compared. The base pressure divided by the nozzle exit pressure was constant for each plume specific heat ratio, regardless of the freestream Mach number and the jet pressure ratio, until flow separation. Therefore, the relationship between the average base pressure divided by the nozzle exit pressure and separation point could be obtained.