Subsonic ambient stream interaction on flow characteristics around a single expansion ramp nozzle

Abstract

In the present study a single expansion ramp nozzle (SERN) system is studied with nozzle pressure ratio (NPR) of 2.9. An interaction of subsonic ambient inflow with M∞ of 0.4 which is induced during take-off of a typical hypersonic vehicle with SERN is considered. Different ambient angles of attack of 0°, −5°, −10° and −15° have been studied. Results obtained by numerical computation are validated by available experimental data. A significant amount of separation is developed at the walls (on both ramp and flap) due to shock wave-boundary layer interaction (SWBLI). Due to the ambient inflow at different angles of attack the separation patterns changes from restricted shock separation (RSS) to free shock separation (FSS). This transition happens when angle of attack changes from 0° to −5° at ambient inflow Mach number of 0.4. Due to ambient stream interaction shock wave oscillates and wall pressure distribution on both ramp and flap changes with time for different ambient inflow conditions. This flow field instability is expressed by the distribution of root means square (RMS) value of pressure over ramp and flap. The main purpose of SERN is generation of thrust of hypersonic vehicles. So thrust and thrust vector angle are important parameters of SERN. Thrust and thrust vector angle of SERN is related to separation pattern. This study gives an insight to the flow structure in SERN when there is a strong ambient inflow and can be very beneficial to the design and performance analysis of SERN.In the present study a single expansion ramp nozzle (SERN) system is studied with nozzle pressure ratio (NPR) of 2.9. An interaction of subsonic ambient inflow with M∞ of 0.4 which is induced during take-off of a typical hypersonic vehicle with SERN is considered. Different ambient angles of attack of 0°, −5°, −10° and −15° have been studied. Results obtained by numerical computation are validated by available experimental data. A significant amount of separation is developed at the walls (on both ramp and flap) due to shock wave-boundary layer interaction (SWBLI). Due to the ambient inflow at different angles of attack the separation patterns changes from restricted shock separation (RSS) to free shock separation (FSS). This transition happens when angle of attack changes from 0° to −5° at ambient inflow Mach number of 0.4. Due to ambient stream interaction shock wave oscillates and wall pressure distribution on both ramp and flap changes with time for different ambient inflow conditions. This flow field...