Computational Analysis of Serpentine Nozzles

A serpentine nozzle directs the jet engine exhaust through bends, to improve flow characteristics and reduce thermal signature, incurring a slight thrust penalty. This property of serpentine nozzles is beneficial for military aircraft operating in hostile airspace, as it improves stealth characteristics. The present work aims to develop a serpentine nozzle model and simulate the flow characteristics using a computational tool. The computational model has been validated against literature data. Four different inlet and outlet geometries have been investigated at Mach 0.9 at 2000 m AMSL. The effect of changing these geometrical parameters on pressure contours and velocities has been analyzed. Based on this study, a cambered rectangular inlet serpentine nozzle is optimal for the target application. Computational results indicate that, for serpentine nozzles, increasing the exhaust velocity after a certain threshold, based on nozzle geometry, leads to unfavorable pressure characteristics. Furthermore, reducing the exit area 0.5 times when compared to the inlet area allows for the best possible expansion characteristics.