Influence of flight mach number on minimum length single expansion ramp nozzle flow characteristics

Abstract

Single Expansion Ramp Nozzle (SERN) has emerged as an option to mitigate drag effects in high-speed flight regimes. This work investigates the influence of flight Mach number (M _∞ ) on the flow and performance characteristics of SERN with Minimum Length Nozzle (MLN) ramp contour, which has not been explored with regard to these aspects. A computational study using compressible Reynolds Averaged Navier-Stokes equations is carried out over a range of M _∞ . In contrast to straight ramp contour, the SERN with MLN ramp exhibits flow separation throughout the investigated range of M _∞ = 0.0 to 2.5. A complex shock structure involving an extra shock is observed for the investigated lower two M _∞ for MLN SERN. For both the straight ramp and the MLN ramp, the trends shown by the coefficient of thrust are found to be similar in the subsonic regime. However, the transition from subsonic to supersonic streams shows drastic increment in coefficient of thrust as well as lift for both straight ramp and MLN nozzles. Furthermore, in the supersonic range, a continuous increment in coefficient of thrust is observable for MLN SERN beyond M _∞ = 1.0. The coefficient of lift obtained for the MLN SERN shows an increase of around 62.5% over those obtained for the straight ramp.