Effects of passive cavity on high pressure ratio single expansion ramp nozzle

The flow control method of single expansion ramp nozzle (SERN) was investigated based on passive cavity, and the effects of passive cavity on internal flow field and performance of SERN were numerically investigated under over-expanded condition by solving Reynolds average Navier-Stokes equations, with adoption of standard two-equation k-ε turbulent model. When the pressure ratio value equals 8, the results show that the passive cavity for SERN has evident effects on the flow field structure by encouraging stable separation and affecting pressure distribution on upper expansion ramp wall, thus improving by 1.75% of the axial thrust coefficient of SERN as compared with baseline SERN, meanwhile the nose-down pitching moment does not get worse. Within the range of 3 to 13 of pressure ratio, the passive cavity can enhance the separation of boundary layer near the passive cavity for SERN, and improve the performance of SERN by decreasing the number of shock train and increasing axial thrust coefficient of SERN and pressure peak value distribution on upper expansion ramp wall.