Numerical Study on Sonic Underexpanded Co-flowing Jet with Varying Separation Distance

Mixing characteristics of sonic under expanded co-flowing jets are analysed with varying separation distance. The separation distance is defined as the distance separating the primary and secondary nozzles. The varying separation distance is understood as a passive way to control a jet. Reduced separation distance value of 3 mm and a dominant separation distance value of 15 mm is used in the current study. The nozzle pressure ratio chosen for the study is 5. The centreline total pressure decay, contours of total pressure, Mach number, density gradient, and turbulent kinetic energy were studied. The present study has been validated with experimental results available in the open literature. Results show that the secondary jet elongates the primary jet potential core length for the reduced lip 3 mm because the surrounding jet shields the central jet. The potential core length for the dominant lip 15 mm is reduced because the surrounding jet vigorously interacts with the central jet due to increased lip thickness. The contours show the jet mixing phenomena such as the wake region, sub-atmospheric region, recirculation zone and shock crossover, Mach disc, Shear layer amidst jets, shear layer between surrounding jet and atmosphere. The characteristics like potential core region, jet spread, Primary and secondary jet interaction and sub-atmospheric region are studied.